With stand-up, I just get in front of an audience and talk about things that interest me. It could be anything: the structure of a wooden cabinet, how air works, the world, knowledge and history since the beginning of the universe.
What I do is this roll-over thing, where essentially I get on stage with the previous show or performance - which I might have done the night or even the year before - as a backup. I'll try to be totally unblocked, and to make conversation and go off on tangents with whatever comes into my head. It's improvising - you need to have your mind open and just unload.
I get quite fascinated by supermarkets and by fruit, which I've talked about in my shows. I'd noticed that I tend to buy fruit and let it rot, so there's this buying, arranging, watching it rot, chucking it in the bin thing going on. Your observations need to be something that people can relate to, for the audience to pick up on it.
If they don't pick up on it, then it's an observation that obviously only I have made, rather like someone saying, 'You know how it is when Dad comes home and he's covered you in marmalade and he's hitting you with a biscuit barrel and then drives a forklift truck into your bedroom and says, "How's that for an invasion of Tunis?",' and you go, 'Nooo, I've never had that experience.'
(picture taken on one of the balconies of the Royal National Theatre - South Bank SE1/ thanks Mimi for the pic and the info)