1) Scan your novel for a piece of writing that stands alone - this is tricky, but it's very important. However short your reading is, your audience needs to feel that they have heard something with a beginning, a middle and an end.
2) Have some cards with your novel's info on it to give out - people came up to me after my reading and it was brilliant to hand out a card rather than relying on their vague memory to recall who I am and what my book was called when they next buy something on Kindle. And writing the wording for your business focusses you - you have to think: what is the salient info about my novel; what might make people buy it?
3) Write an intro to the piece and a sign off paragraph. Even a short intro will help readers engage with you - telling them what you were up to at the time of writing the piece can work well, as can any behind the scenes info about the writing/researching the piece. As a sign off, I always thank people for listening, remind them where they can find my work.
4) Print out the piece you've chosen, read it aloud and time yourself. You don't want to read for longer than 10 mins. Mark paragraphs and sentences that you could lose, if necessary. I always have some marked out and if I think things are dragging, I do the shorter version.
5) Edit your piece. There are two reasons for doing this: Firstly, it might need editing to make it a successful standalone piece of writing - tinker to make sure that everything your audience needs to know is there for them. Secondly, it's wonderful to take the opportunity to focus on some writing that was signed, sealed and published. You will almost definitely find ways of improving it and you can add the edit to an ebook instantly.
Bye for now