In the early 90s I met Jimmy Tarbuck backstage at a show. I told him I was a struggling comic. "Good luck!" he said as he puffed on his cigar, "comedy is the hardest job in the world!"
I don't agree with Tarbuck. It's not as hard as being a fireman or a brain surgeon or in the SAS or (given that you work for 20 minutes a night and then get drunk), as hard as working in an office. Still, most people would rather eat their own liver with some fava beans and a nice Chianti than perform stand-up comedy.
At its best, stand-up comedy is the purest and most immediate medium for comedy and possibly even self-expression. What other outlet allows you to have an idea in the afternoon and then try it out that evening to an actual audience?
The jokes, although important, are not in themselves enough. You need to be able to appear relaxed and confident, control the room, think on your feet, involve the audience without letting them steal focus from you, and adapt your style and material to dozens of different, difficult scenarios. The only way to gain these skills is to get up on stage and do gigs. As many nights a week as you can. Probably for at least five years.
All those things will come to you, if you have the right stuff. So if you're starting out, then what you need to concentrate on is your material. Most clubs have an open spot where an unpaid wannabe can do five minutes. The audience will be quick to judge you and you're trying to get booked, so start small. Write a five-minute script (don't overrun), with a punchline every 30 seconds, with your best three jokes at the start and another belter at the end. Make sure that the jokes are original. Make sure you know exactly what you're going to say. Practice and be prepared for failure.
Once you feel comfortable on stage you might have the confidence to try out stories or even to reveal your personal secrets. Be truthful and funny will come.
You will also find that you do a lot of your "writing" on stage. When you are in the zone you find you can leave behind the script and just chat. Inspiration strikes and you discover new avenues, even in well trodden routines.
Josie Long on writing for stand-up
If you want to start writing stand-up, try not to feel like there are any conventions you have to subscribe to. There are no established rules as to what your show should contain.
Try to find your own voice. Think about what you find funny and what you would want to see if you were watching. It's not helpful to second-guess the audience's tastes in advance. It's better to take risks and perform material that may not work if it is something you genuinely think is hilarious. Everyone has bad gigs and through them you will develop and evolve as a performer.
All of that having been said, it's good to be economical with your material. Only use things you feel are essential. It's not just about enjoying yourself onstage, but about finding a way of conveying your sense of humour to other people.
Try as many different ways of writing as you can, and try to write as much and as often as possible. Don't decide against trying a joke because it doesn't fit the style you've chosen for yourself. Include any ideas for jokes you have.
Write at home on paper, steal your best conversations, do specific research, write by speaking out loud on your own, play writing games, take good ideas onstage then bat them around and improvise, note down things you see or are struck by ... you never know what will develop into a longer routine or piece.