The same advice for bidding on Priceline can be applied here. Research the market before bidding! I assume that on Hotwire, like on Priceline, you big on zones in cities. Look up the major hotel chains in those cities, and see what sorts of rates you can get. Then don't bid higher than you could find online. It's that simple.
It amazes me how many people have the same 'complaint' about these name-your-own-price sites: that they bid for a room, got a room, and then looked and saw the hotel had cheaper rates available. Why are you bidding for a higher amount than you could book yourself? A little research in advance can prevent this. Don't have time to do the research? Well, then consider four bucks the fee of convenience.