Things to include in your pitch:
1. Who - as in the protagonist and their personality at the beginning of the story to serve as a baseline such as quiet, tomboy, etc)
2. When/Where - the setting, background
3. Why - inciting incident, the call to action
4. What - the stakes. What drives the story?
5. Hook - end with the promise of more action
Research market, category, genre, age group
Mention similar titles based on tone (not comparisons like my book is the next Harry Potter, instead my book will appeal to the readers of... or something along those lines)
For an elevator pitch, you need the MC + call to action + the challenge they face. (so the Who, Why, and What)
I've pitched several times face-to-face. With 3 agents and 1 editor. All of them requested pages. I've also gone to the Long Island Romance Writers Luncheon twice and pitched to agents there, although that pitching is more of the elevator kind instead of a sit down. The nice part about that is that all of the agents I spoke to said to send the project so I did (according to their guidelines) and was able to mention meeting them in the query letter. Each one then gave me a personal response (no form rejections).
I think the biggest keys are being calm but enthusiastic about your book, and using the time wisely. Have a dialogue with the agent instead of giving a long speech. It will take the pressure off of you. Trust me.