The most important thing is to write material that YOU think is funny. If you don't think it's funny, but you're convinced that other people will think it is, well they won't.
When the first-rate author wants an exquisite heroine or a lovely morning, he finds that all the superlatives have been worn shoddy by his inferiors. It should be a rule that bad writers must start with plain heroines and ordinary mornings, and, if they are able, work up to something better.
It seems to me what is called for is an exquisite balance between two conflicting needs: the most skeptical scrutiny of all hypotheses that are served up to us and at the same time a great openness to new ideas . . . If you are only skeptical, then no new ideas make it through to you . . . On the other hand, if you are open to the point of gullibility and have not an ounce of skeptical sense in you, then you cannot distinguish the useful ideas from the worthless ones.