Bring this success picture to your mind each and every time you think of your presentation. OK, you've got the fear monster into the cage. Now you need to lock it in tightly. And the first way you do that is to reclaim the breathing technique you had when you were first born- breathing from the diaphragm. Your mind goes blank and your hands tremble when presenting because your brain and muscles are hungry for the oxygen they need.
Diaphragmatic breathing takes care of that.
It also gives you a base for a voice that carries well without a microphone. When anxiety hits, you tend to breathe in short gusts using your chest muscles instead of your diaphragm. Often, your shoulders will move, alerting you to the problem. You have barely enough breath to speak a few words, to say nothing of sentences. Breathing with your diaphragm will counteract this.