I had never used Priceline or Hotwire up until a few months ago but now, I will never book another hotel without them. You will save 50-60% by using Priceline ( Hotwire is usually a bit higher)
There are 2 forums similar to this one, except they are exclusively dedicated to the ins and outs of Priceline and Hotwire.
biddingfortravel.com is the biggest and most comprehensive one and I use it alot but the owner / moderator is a real piece of work and loves to ban people for no reason. I got banned myself and still havent figured out why. I opened a new account to ask why and got banned again with no explanation. I had to change my IP address so i can still browse the site at will. I just cant post there.
The other one is betterbidding.com. People are nicer but its not as big so theres not as much info.
Basically you bid for a hotel at Priceline but dont know what hotel you will get until your bid is accepted. You choose, what city you want, what zone within that city and what star level of hotel and then bid. I never used Priceline before I found those travel forums because there was too much uncertainty involved. When you visit those sites, you will see that you can do alot of research into which hotels commonly come up when you bid. For example: You can search San Francisco, then search the Nob Hill zone and see the same 2-3 4 star hotels come up over and over so you can be reasonably sure you will get one of those hotels when you get your bid accepted. You can also see how much people are bidding and what bids are getting accepted so you dont bid $125 for a room thats listed at the hotel website for $200, when you couldve gotten it for $90.
Hotwire is similar in that you dont know what hotel you will get, but you dont bid. They just offer a hotel at a certain price and then you decide if thats acceptable before you know which hotel it is. Again, you can narrow it down by using the travel forums.
One thing to watch for is that Hotwires rating system isnt exactly the same as Pricelines. A 3* hotel at Hotwire will tend to be a 2.5* at Priceline so it can be hard to make a true comparison sometimes.