When it comes to public speaking or presenting in front of a huge audience, the more you face the public the better you get at speaking live. Initially you may fumble, you may develop those nervous sweats, but once you keep repeating your acts, you subconsciously develop that skill.
I had been teaching many students from a very young age, i.e. since I was just 16 yrs. I had developed the skill of interacting with the audience while I used to teach. The duty of a teacher is get your thoughts across your students in the most effective manner possible, the same goes for a presentation too; in fact teaching itself is a form of presentation.
The moment you go for by hearting your presentation, you generally fall into the most likely trap of developing the fear of forgetting your presentation. Use your presentation slides as an aid to remember points for your presentation, the rest should be there in your mind, which you can explain the way you feel comfortable with. Always remember the more you are comfortable with the presentation, the more effectiveness is added to your presentation.
Interact with the audience and add liveliness to your presentation. Give your presentation a form of discussion. The more you involve your audience the better response you receive and this leads to boosting your confidence. Being formal is a part of a presentation but slight informality adds life to your presentation, and shapes it the way you wanted it to be.
While making a presentation always remember that, if the audience has knowledge of about 10% on the topic of your presentation, then after your presentation they should know at least 75% of the topic. This is possible only when you have adequate knowledge of the topic. Superficial preparations generally tend to cause the unnecessary nervousness. To speak 10 words on stage, you need to know 100 word of your topic.
Finally get yourself charged up before the presentation. You only have to say to yourself repeatedly that I have worked for this presentation and right now I just want my efforts to bear fruits, and nothing can stop me from doing that. When you have developed the required passion for your presentation, it reflects in your presentation, and your thoughts are effectively conveyed.
Also when you develop the required skills for presenting, which should come with practice, do not give up presenting whenever you get a chance to do so. A break as long as 3-4 months can also make you develop cold feet after facing the audience after a long time. So it's better to always keep the ball rolling.