Well, krykos and mike wanted to know...
This is actually a very big process (in terms of filesize)
first step is you need an uncompressed videofile... flash has a very lousy video compressor so all compression should be done with another program.
If you have a mac, it becomes an even easier process, because you can import swf files into final cut pro and compress it via that.
But, windows is alot more time and hard drive consuming.
First of all, make sure there are absolutely no movieclips in your animation (as they will not be animated in the video)
then you simply go File > Export > Export Movie...
Then you choose AVI format and your filename... keep the movie dimensions as close to the original as possible, but if you're just exporting for youtube, then a width of 480 is fine.
do not compress the video, and keep audio to either 44KHz 16 or 8 bit stereo (unless your audio isn't stereo, then mono is fine also)
WARNING when i did this for my joker and the thief video, the final filesize was nearly 5gb, so just warning you if this is a problem.
After that you can use any video compressor program you want.
DVDVideoSoft has a great range of freeware video and audio programs, and are so simple, small, easy and above all trustworthy (free from spyware, virus and everything malicious)
so i used their program
Video to Flash Converter to get the video into a FLV format. also, due to the way it was programmed, compresses the video to a filesize suitable for different video sites to stream, including MySpace Videos, YouTube, Google Video and whatever you want.
This brought my Joker video down to 30MB, which is fine by me, because its FLV when YouTube compresses it further not much will change and you still get the same high quality video at a smaller stream size (and doesn't compress it to a completely different compression format)
So that's it really, doing it this way will reward you with original quality video and audio ready to be watched on your favourite video streaming sites