first go to www.biddingfortravel.com and click on Missouri - St. Louis and see what people are getting on priceline.
Second, pull up www.hotwire.com and put in the dates you like and see what the hotels are going for on Hotwire.
Use the two figures to gauge how you will bid on www.priceline.com and maybe bid a few $$$s less than hotwire but stay within a few dollars of what you saw on BFT.
I've found priceline to be risky, but BFT always makes that risk so much less as I have an idea of which hotel I am going to get.
hope this helps!