Most students panic when they have to give presentations in front of an audience. My suggestion is to first study some of the fixed expressions used whenever you have to give a presentation.
Below you will find a variety of links on how to give an effective presentation.
English Club ;Gives you the vocabulary to use in every step: Introduction, Preparation, Equipment, Delivery, Language, The presentation, Review, Test.
Better English :Improve your presentations by taking a look at grammar exercises related with presentations.
Learn English Today: Useful Phrases, Presentation Vocabulary and Presentation Basics.
Giving oral presentations: The homework task in this site contains more than 9 hours of self-study. It´s very complete.