Best way to match minifigs and tell what set they are from?
One way to do this would be to look through the Bricklink categories for minifig torso assemblies and minifig leg assemblies. There are a lot of them, but once you find the part you are looking for, you can then learn what set it came from which should lead you to a couple of complete minifigs (click the part id then click the "View" link under "This Part Appears In" on the right).

You could also search through the Minifig category on Bricklink.

You can go through those categories by year if you know approximately how old the parts that you have are.

If you get stuck on something, feel free to post the picture in a new question here. I'm sure that someone will recognize it. :)