Your question is a VERY popular one. To get some info, start perusing the list of Posts in the Basement and Attic Forum (which is the Forum you're in now.) Just down from your Post is one that's a good start. There are a LOT of others! And to boot, go to the NEXT Web page, and the one after that for even MORE info.
I'm not trying to dodge your question. It's just that I, personally ..., have answered this question a great deal. My fingers are getting worn. Just don't stop after reading the 1st or 2nd post. The more you read, the more you'll learn! Oh, and look for posts that talk about basements as well as crawlspaces. Although the question may not be EXACTLY like yours, the info therein may be exactly what you want/need to hear.
My best to ya and hope this helps.
Jay J -Moderator
PS: God Bless America!