Need help on purchasing homes through foreclosure?

I'm interested in purchasing homes through foreclosure. I know nothing about the process. I visited my local courthouse today and looked at homes on the foreclosure list; but here are my questions: does a person bid on the property? with whom do you speak about (any) taxes or leins and whatever else is owed on the property? who is actually selling the property: my county? the bank with whom the loan was defaulted? if there's a resource online, it would help. i don't want to get burned.