Here are a couple of links:

http://www.morphography.uk.vu/modtut1.html

http://www.nerd3d.com/Tutorial/Conforming.htm

With armor, it's sometimes better to make "smart props" instead of conforming clothing. That is easier, too.

There are also tutorials you can buy. Probably the most popular are PhilC's CD, and Markdc's video tutorials.