I found a great web site which helped me book a hotel through priceline.com for my trip to San Juan in November 2003. It's called BiddingForTravel.com. As stated on their web site, "BiddingForTravel.com's primary goal is to promote informed bidding when using priceline.com's (US) travel products." Included on the web site are FAQ sheets on how to bid for hotels and airfare; list of hotels (not inclusive) that have received winning bids and also categorizes them in 2, 3, 4-star or restort categories; discussion boards of those wanting bidding information and of those that have posted their winning bids.
You can easily search a particular city and see which hotels have had winning bids in a particular category (e.g, 4-star hotel). From there, you can get an idea on what price to bid. Post your request for a bidding strategy following the rules and you will receive bidding advise.
For my Baltic May 2005 trip, I bid on a hotel for London and ended up at the Thistle Charing Cross hotel for $125/night (regular price $380). Excellent hotel and location!
If you work closely with the folks on Biddingfortravel, you should be able to get good hotel deals!