Once you have a booking, start looking through your notebook for bits you want to perform. Also start to plan for all the things that could go wrong, like getting heckled or having an inattentive audience, and try to figure out how you would handle the situation. Chances are that you won't encounter any on your first set, but you might as well be prepared.
Organize your jokes into a set list and start practicing — but not memorizing — your act. Time yourself, factoring in time for laughs, so you don't go over your time.
Make sure to videotape or audiotape your set and record your observations in your notebook. You'll see where you need to fix things, but focus on your successes and build on them!