There is only one thing you must learn in order to master public speaking. That is speaking extemporaneously. Although the definition of that word is, "Spoken or done without preparation", I don't believe that definition to be correct. What speaking extemporaneously means it to speak without referencing notes, slides, etc. You can prepare just as long as your preparations are internalized and then discarded for the speech. Once this technique is mastered, nervousness goes away because you know what you're going to say generally, and confidence can be easily built by successive well-delivered speeches.