In order to reduce file size, Ive been using Handbrake to reencode video from my mobile and hd camcorder to m4v files with a bit rate of 4000 kb/s to ensure the hd resolution is retained by Youtube.
Using fast deinterlace as well for the stuff from the camcorder.
What encoders are you guys using, the format and your settings for non hd/hd files?
Cheers