1. Don't begin every sentences this way: "In my novel..." Especially true when you're with a bunch of other authors and when you're serving on a panel.
2. Don't pay attention to what others are saying about their own books and immediately chime in about your own.
3. When at a book festival don't run around to each author and spend big blocks of time telling them all about your book instead of staying in your place to talk to possible book buyers.
4. When at a book festival spend all your time visiting with your neighboring authors and not even paying any attention to people who stop to look at your books.
5. When you at a writer's conference, sitting down next to someone and not asking them anything about themselves, instead immediately launching into an lengthy description of your book.
6. Not bothering to hand out your business cards or bookmarks to anyone no matter where you are.
7. When you are on a panel, taking over and not giving any other author a chance to speak.
8. Thinking you're more important than anyone else in the room and making sure everyone knows it.
9. Telling the whole plot of your book to anyone that will listen instead of a short two sentence description that might intrigue the person.
That's all I can think of at the moment--anyone want to add anything?