You never heard of that huh??

Here's the first link that came up on google, http://www.misterfixit.com/dyncompr.htm
This guy's write up is alot better then me explaining it to you. When I do this test I basicly look for 50% difference between static and running. That's a good indication your engine is okay. Also you could do a wet compression test as well if you want to get the whole story.