How to lose google ranking

Got a auto repair site that has just lost ranking on google, what could have caused this - I ask as I have used every black hat trick in the book to get it were it was, now I need to know which ones would have caused google to black list me..

Any ideas so this does not happen again.

are you deindexed or just devalued? How many sites did you have indexed and how many do you still have indexed?

All pages from my site removed, had hundreds indexed.