Since it is a subject you are very familiar with, don't try to write a word-for-word speech, but it's important to at least have a good outline to make sure you don't miss important points. Otherwise, you end up stopping in the middle of a story saying, "Oh, I forgot, I needed to tell you about...".
For the technical stuff: make sure you practice firing up your PC and software
or overhead projector, etc. so you not only know exactly how they work
, but are so comfortable with how they work
that it is second nature. Get there VERY early and set everything up and test it to make sure there are no technical problems. If you are doing it by PC, put shortcuts on the desktop
for what you need, so you don't have to drill down through directories hunting for stuff.
If you make a mistake, laugh it off. Audiences are forgiving unless you take yourself too seriously. Basically, if they like you and you seem human, they will tolerate a lot. First thing I learned in speaking seminars is it's perfectly OK to make a fool of myself as long as I let the audience know I know
I look like a fool and it's OK for them to laugh at me.