where can I learn about keeping compression settings within standards?

I end up having to use WMV mostly because people want to be able to throw a video in powerpoint. I'll create a clip using the standard WMV 720p30 setting, then someone just wants it smaller. Ok, so I adjust the bitrate down to something that still looks "good enough", adjust the audio down since my starting audio probably wasn't that great anyway, and compress.

Sometimes the files play well, and sometimes they don't work at all. I have similar problems with mp4 format.

Is there a book I can read or a class I can take? It seems like trial and error. And often times something works on my computer, but not others....with the Same format, but Slightly changing a couple numbers.

This definitely seems to be something I should be an expert on, but I am probably only an novice at best.

Any suggestions?