Yep...abc_n_xyz is right...you need to know the material that you are going to present inside out. Understand your audience well and have a feel for what they want to hear from you. Practice, practice and practice with a friend or in front of a mirror. And what's the worst that can happen if you screw up...you will still wake up the next day. Look at it as a learning experience and over time you will master your presentation skills. The audience does not care about your accent if you have one...just focus on getting your point across and you will be fine.