I'm similar to you Jesper in that it does seem to take me a disproportionate amount of time to prepare for a presentation. I don't consider myself a very good speaker and it certainly doesn't seem to come naturally to me so my coping mechanism for that is extensive preparation. My tool to not 'freak out' on the day is to not leave anything to chance. Necessary ad-libbing is a definite no-no.
My last presentation, just before xmas, was a pair effort. Our approach was to start off by writing down everything that came out of our heads onto index
cards and have them laid out on the table. Each time we came back to do some more prep, an hour or so at a time, we'd roll out the
cards and talk about them. Some got binned, some new ones got added. Eventually the cards would be put into some sort of order, we'd practice talking through the cards out loud as if we were presenting them to gauge time and to flesh out any disconnects in the flow of conversation. More cards got canned to trim down the time.
Then we put together a visual presentation using KeyNote on the Mac, nothing too heavy, no bullet riddled corpse. Just enough to act as a visual aid to the verbal content. In our case a good dose of nerd humour Meme's were included just to keep the mood light.
One of the most valuable things that I learned about this process was that I'm pretty sure that I would not have been able to come up with as good a presentation on my own. Having two people working on it made a huge difference. We have pair programming, why not pair presentation prep? We have some more technical presentations to do this year and it is my intention to prepare the content for them with a colleague even though the talks will be delivered by a single person.
As far as becoming more efficient... I think that'll just come down to practice.
Edit: I'm not sure this qualifies as Meaningless Drivel but I don't know where else it could live? We don't have a
Soft Skills forum.