An agent's advice on doing a "pitch slam" at a writers' conference:
Don’t talk the whole time during a pitch. You should be able to do your sum-up in under 2 minutes (and if you can’t, you know you have a problem). Then allow the agent time to ask you questions and to get to know you. We are just as interested in seeing if you, as a person, would be a good fit for the agency.
Yes, we know you’re nervous but treat the pitch like a job interview. Fake it till you make it with your confidence. You’ll come off professional and we won’t know the difference. We like professional, confident authors.
The pitch is not the start or the end of your writing career. Don’t treat it as so. It’s just one facet of this whole business.