The only thing you need to write something publishable (poem, story, novel, memoir) is lots of paper, a pen, a big library (either your own or someone else's) and lots and lots of time in small or large pieces. Oh, and the seat of a chair, to which, as Wodehouse put it, you need to apply the seat of your pants for all that time. There are vast numbers of highly successful writers, and utterly brilliant writers, and writers who are both successful and brilliant, who have never taken a course and will say so publicly.
But after the festival session, over the green room glass of wine, you will discover that although they've never taken a formal course that doesn't mean they've never sought and found what you get on a course. Maybe they had a senior writer as a parent or a friend or a teacher. Maybe they studied for a literature degree and managed not to be too daunted to write their own stuff, but instead turn all that educated reading into intuitive writing. Maybe they were bold and wrote off to a writer they admired and were lucky enough to acquire them as a mentor. Maybe they found or founded a writers' circle with exactly the right combination of rigor and supportiveness, in exactly the right kinds and levels of writing. Maybe they were lucky and their promising early effort was spotted by an editor (back in the dinosaur age) or an agent (more recently) who was prepared to be patient and able to be a mentor: the risk of that is that the writer gets published, as it were, too early, and has to do their writerly growing-up in public. And if you're well-wired for learning from the printed page (and by definition a writer-in-the-making probably is) then it's possible to learn a lot about writing without talking to another human being. Maybe the non-course-doing writer turned to the how-to-write books and had the confidence to accept, adapt or ignore each piece of advice in just the right way. Maybe they were born with just the right interaction between analysis and intuition, and managed to deduce and put into practice everything they needed to know from the novels/poems/stories/memoir they read.
But all these things are hit-and-miss: you need good luck and good timing, and huge perseverance to keep going alone in between the lucky moments (not that you don't need perseverance the rest of the time too, of course). You also need confidence, and/or a handy family tree or connections, to make the most of possible help, and tact and confidence again to discard it if it's not right for you. Whereas the right course, at the right moment, can make you a better writer, faster, than you ever could on your own, because you'll be learning in a systematic, integrated way, so that it forms a virtuous circle, a positive feedback loop.
On a good course you’ll learn many things: to read as a writer, without which you'll never become a writer worth reading; to find material in the world and use it well; to find material in your imagination and your self and develop it; to sharpen your technical tools and acquire more of them; to integrate technique and intuition; to survive the ugly duckling stage while they're still integrating; to cope with feedback so you're neither shattered by criticism nor blinded by praise; to make your own judgements about what to accept, what to adapt and what to ignore of what you're taught, and what is said about your work; to read your work as others do both by listening to those others, and by giving feedback on their work; to understand the value of your writing as writing, and the very different value it might have or not have in the marketplace; to set about getting your work out there, and survive.
A good course should also be a safe space to experiment and dig deep in your past and others', to make mistakes, to fail. It's also hugely valuable as a way to meet other writers, and share support and information, although with the online world that's more available to everyone. There's all the difference in the world between the wonderful affirmation and support you may get from a non-writing partner or a loving parent who never reads a book, and the reactions of people who know what you're trying to do, know that it's difficult, and can talk intelligently about where you've succeeded and where you haven't... yet. A good beginners’ course will help you to find your writing self: will show you the road and give you some maps and equipment to begin travelling it. An advanced course may not only get your writing to publishable standard (although no course can guarantee publication and you should steer clear of any which claims to) but should also arm you for the ups and downs of the professional writing life. The better you understand your writing and the sharper your technical toolkit, the more able you’ll be to turn your hand to new projects when economics demand it.
Another reason not often cited for doing a course is the way that it can legitimise the time you spend writing in the eyes of your non-writing family and friends. For many of us, particularly if your temperament (or society) expects you to put your own needs last, it's much easier to claim the time and space and quiet you need if it's part of a course, perhaps leading to a certificate or qualification, than if it seems like pure selfishness, unsociability and general neglect of partner and children. And at the higher level having an MA, for example, does tell the slushpile reader that your manuscript will at least be competent and worth a second look.
But is it the right moment? I think it’s best to wait to do a course till you’ve got as far as you can on your own. That doesn't mean you must wait until you've got a library's-worth of rejected manuscripts under your bed and you're contemplating a Masters. But if you turn up at a course - even one aimed at beginners - having never written a word, then you're not well placed to decide if it is, actually, the right course. You're also at risk of ending up writing like everyone else on the course. As a raw beginner rules are immensely reassuring, and there are enough teachers and judges around who cling to them that it's very possible to go a long way while conforming to them. But it won't be your way. Whereas the longer you leave it to take a course, the more you'll know about your writing and your writerly self, and can decide what challenges or criticisms or advice to accept, what to adapt, and what to ignore of what you're being offered. Good teachers do their best to bring out your own best writing, but we all have our limits, and too many are too rule-bound, and have too fixed an idea of what the best writing is like. Other teachers don't have a fixed enough idea, in the sense that they can't offer you enough technical understanding to help shape your material and develop your craft.
And is it the right course? That's another reason for getting to know your writerly self before you begin to look for one. One-off courses for a day can kick-start you, inspire you, and introduce you briskly to lots of tools, and then you must go home to learn to use them. They're very unlikely to turn you into a clone because there just won't be the time, but you will then be on your own. The same is true of single weeks (Arvon, for example), which can be incredibly inspiring in a mad, hot-house sort of way. Once-a-week for a term or a year can be found at your local university, HE or FE colleges, and places which specialise in adult education, such as City Lit and Morley College in London. Most MAs have this shape. These longer courses are great for giving you a reason to write, for trying out different forms and ideas including unfamiliar or daunting ones, or for supporting you while you develop a longer piece, but some are, again, more narrow-minded than others in the kinds of writing they admire. Equally, a course which has a huge range of genres and levels may not have anyone else who, for example, knows anything about fantasy, or short fiction. There are distance and online courses (Open University, Open College of the Arts, and even some MA courses); there are courses in holiday places which can also be incredibly energising: Skyros, Crete, Spain. The writing magazines such as Mslexia and Writers' News have lots of advertisements. It's also worth having a look at the structure: a full time course might seem more desirable if you could afford it, but it can be almost too intense, without enough time for each week's new stuff to bed down and develop and be integrated in your work, before the deadline for the next workshop.
What is the focus of the course? Most will have a mixture of activities, but some do a lot of writing in class, while others concentrate on critiquing, which you might find almost as good and much cheaper in a real-world or online writers' circle. Is there lots of homework? How much scope is there for doing your own thing, which might be just what you want, or mean that the classes are too unfocussed. I would always suggest that if you can't work it out from the information on the course, you talk to someone, to get an idea of what the classes will be like, how much work will be expected outside them, and so on.
Is the teacher published? At anything beyond the most basic level I do think they should be published, but it's certainly not true that big writerly names published by big publishing houses are automatically better teachers. And given the peculiar economics of the book industry the fact that someone's work isn't publishing now doesn't mean they're no good, as either writer or teacher. Is the teacher experienced? I've said that a course should be a safe space, but it's a delicate balance and it's chiefly the teacher who must find it: a workshop which is vicious in the name of rigour can destroy your confidence; one which is anodyne in the name of supportiveness is little more use. The seminar bully is a known phenomenon, but it's particularly painful in a discipline such as creative writing, which is so personal and often involves sensitive material. It's also not much use if no one ever utters a word except that they liked the piece, from lack of confidence in critiquing or simply apathy. On the other hand, you must be willing to be challenged. If you have a very delicate stomach for sex or violence, or are a particularly die-hard anti-sexist or anti-racist, be aware that perfectly legitimate writing may offend you, whether it's the group's work, or readings that the teacher brings in. If your gender politics, race-relations or other politics haven't been updated in a while, be prepared to find yourself causing offence in ways you didn't intend. If you have very particular reasons for finding a topic distressing, do mention it to your teacher in confidence at the beginning: experienced teachers have ways round these things.
All being well, the right course may be the thing which catapults your writing up one or more levels and even into publication. Courses can change lives. But if it feels really wrong, even when you've started, then walk away, because you must protect your writing self. If it's doing you no good, then is it worth the time, even if you've spent the money? And if it's doing you damage then run, and fast. On the other hand, you must be even more willing to be challenged in your work. Sometimes the thing you resist doing is the thing you should be doing most: resistance is one way the Inner Critic stops you trying potentially fruitful things. A good teacher will ask you to go a bit beyond what you think you can do, will gently encourage you out of your comfort zone, because that’s where the really exciting writing comes from. If the course is a safe space, after all, it doesn't matter if you fail or embarrass yourself, or even distress yourself and others, if it's by way of becoming a better writer.
One thing to remember, though, if you're considering a course, is that the results may not be immediately apparent. Indeed, for a while during a course you may feel your writing is worse: you're trying to integrate new techniques and new ideas with your old intuitions about how writing works. And it can lead to a very ugly-duckling stage, all awkward and self-conscious, full of false starts, interesting things which don't really work, heroic failures. But as all teachers know, if a thing's worth doing, it's worth doing badly: it's process writing, and that's another thing which courses are for. Often it's stories you wrote after you'd finished the course which win competitions, the novel after the MA novel which sells. But that doesn't mean it wasn't the course which made those successes happen.
And a moral tale: I know of one writer who started a very well-regarded course which is very difficult to get on to and well-known for the diversity of its graduates. He had come from a particular milieu which turns out one particular kind of successful writer, including him. He had quite a track record in competitions and small magazines, but he found that on this course neither the tutors nor his fellow students worked and thought in the same terms as him. They didn't regard the rigid rules of 'good' writing, in which he had so much invested, as the sole criterion by which writing is judged. They thought differently from each other and differently from him, and so his writing was carefully, methodically and kindly challenged from various angles; whether a piece succeeded was no longer a matter of whether it conformed to those rules; it was judged by a much more sophisticated, slipperier aesthetic, based on a wider conception of literature. And he couldn't take it: he left the course in the first term. But what a waste of money as well as time! Not to mention of a place which could have been given to someone else. Perhaps he would say he was right to escape a course which didn't know good writing when it saw it, but I would say that the fault wasn't in that course, but in the rigidity of his earlier training, which hadn't given him flexible confidence, to understand and make the most of what was offered, but only the brittle confidence of the conformist. How much better a writer he might have become, if he had only been willing to try to understand the challenge on its own terms, and explore the possibilities it presented, rather than running away, back to his own narrow world.