Wondertwin...Compression can be its own game. I dont think you can simply give a a straight answer. There are far too many things to consider. Here are some things aff the top of my head. Hope it helps.
1) A general rule in video is you get two of three. Good / Fast / Cheap. Pick two you cant have all three. Compression is all math. the cleaner you want it, the bigger the file, the more detail(color and Luminance) the more complex the math has to be to compress it and make it look good.
2) Codecs are key. Some codecs are free. Some you must pay for. Guess which ones are going to be better. Also see above rule.
3)It depends on whats in the frame, lots of details or small details. Example, I do a lot of talking heads, not much background. Mostly white or a nice gradient. They compress pretty small and fairly good quality, Sometimes I have natural backgrounds. For instance the office a person is filmed in. things in the back ground include, Desk, books, windows, computers...all the crap that could be in an office. These tend to be a little bigger. Maybe not as sharp due to all the details that are starting to show up. The worst video I have ever tried to compress. I had a 60 min video that was all water skiing. Shot on a sony cinealta, edited in a linear HD edit suite. BEAUTIFUL. the location was a river here in Texas somewhere. most of the shots were of a single skiier against a background of moving trees and rocks. Holy smokes that looked bad, The compression was trying so hard to keep all the detail from the trees in the background that it ate up all the bandwidth. The trees turned into pixelated squares and tore up so bad the client looked at me like I was nuts. Needles to say I nor the client was very happy. I think he eventualy had to find some place in hollywood with a dedicated computer to get good compression.
For all those terms and thing use this site
http://www.videohelp.com/
there are some pretty good explanations on here about what stuff is and the terms used in this industry.
one last thing Experiment as much as you can. this is how youll find your best solutions. Good luck.
PS some good compression programs are: apple compressor / Episode / adobe / and some are built into programs such as final cut pro / after effects / premier
First step........ Take the lens cap off.