Imagine yourself in front of the crowd. If you can, visualize the location, where you will be 5 minutes before and during the talk.
See yourself speaking and go through each point that you will share. Imagine each moment that will take place, the words you say and the confidence you will evoke.
Imagine the audience's reaction and the sounds you hear. Be as specific as you can be. Can you hear the rustling of papers or people typing?