Become comfortable with Priceline before you bid. If you are not comfortable, do not bid.
I have used Priceline several times, for hotels only. You get to choose the city, neighborhood, and quality of hotel. So, for example, Orlando, WDW area, 3 * hotel. Then you put in your bid, what you are willing to pay per room per night, NOT including taxes and the $5.95 fee (only payable if your bid is accepted). If your bid is accepted, Priceline gives you the hotel information and bills your credit card immediately. Consider all transactions FINAL. That's how Priceline works.
Savings can be TREMENDOUS but you must be flexible about which hotel you will get and you must be very fixed with your travel dates. I recently got a 3* Hilton in Sacramento for $23 + $10 bonus a night for 5 nights, plus tax and fee. (I paid $23 and Priceline threw in $10 on a promotion they were running, offer expired now). Including taxes and the Priceline fee, I am paying less than $30 per night.
The mentioned websites are good places to browse as you can get an idea about what locations, star levels, and bid amounts are being accepted on Priceline. Study the FAQ on
www.biddingfortravel.com.
A couple tips, my opinions only, bid 3 * and up. These are usually decent to gorgeous properties. I would be nervous to bid 1 * or 2*. Bid only when your travel dates are very firm as you pay whether you stay at the hotel or not. Also, learn how to free bid, as explained in the FAQ mentioned above. This will help you tremendously to not overbid.
Good luck. It is not as scary as it seems at first, you just have to know the rules!!
Peggy