Summarize your book in a few sentences. Keep it as simple as possible, but do hit on any plot twists, major scenes or anything that makes your novel stand out. Mention any books you might compare your novel to.
Practice your pitch with a friend. Iron out any problems before meeting with the agent. Anticipate questions and answers.
Write at least three chapters of the novel and a synopsis. If the agent is interested, he will ask to see more, and you will have something to give him.
Know the agent's area of expertise. Don't pitch your romance novel to an agent that represents only science fiction or nonfiction.
Follow up with a thank you note. If you don't hear from the agent in 30 days, follow up with a letter or phone call.