I love priceline. I am was about to use priceline for my vancouver trip but decided against it. Mainly because there is a special deal at Travelocity, where if you book a hotel for 2 nights using a Mastercard, you get $50. This added to the fact the hotel we were interested in dropped from $108 to $92/night and is again back up at $108/night means we got a steal of a deal.
But back to how to use priceline. There is this website called Bidding for Travel, which tells people how much people have recently bid for rooms in the area you are interested in on priceline.
I looked up the Vancouver area and found that people were paying about $75/night close to the time we were interested in. Also I figured out which hotel they had gotten for that price. The website also has a list of hotels for each star category. This will give you an idea of what hotels you potentially are bidding for and how much others have paid for them in the past.
I use this to help me get and idea of what to bid for the area and star quality of hotel on pricelines. It's a great tool for getting a cheap hotel. Enjoy.