Techniques for preparing are probably unique to each presenter. Some start by writing a paper, and essentially narrating that paper. Personally I make flashcar

Techniques for preparing are probably unique to each presenter. Some start by writing a paper, and essentially narrating that paper. Personally I make flashcards - sometimes on paper, often in PowerPoint. I make a card for every major point (in no order) that i want to cover. Then I flesh those out with ancillary slides. Then I order them to make a narrative. From there I refine it, add more, reorder, remove some, until I can do the presentation from start to end and there are no jarring jumps or omissions. Obviously this is a faster process for subjects I know well, and where I have a specific point to make. It's worth pointing out that it is harder to make a short presentation than a long one. Making a short one takes discipline (cut out the non-essential) and clarity (make your point clearly and with sufficient supporting material.)