I know this isn't going to help everybody, but I know there are people out there who are wondering how to make a preloader, so this is for them. Not people who know what they're doing or don't care and want free BLAM points.
Before you open this up, I'm hoping you have seen some Flash tutorials about how to use the timeline and symbols. I sort of explain it but not very good. I just focused on the Preloading ActionScript part.
This is different than the Newgrounds Free Preloader. It's easier to understand how it works, so it's easier to use this outline to make it your own preloader. It has instructions how to make a loadbar, percent loaded text, and play button.