There’s a decent article on getting the best prices for hotels up over at everything2.com.
Don’t believe every claim 100%, but many of the general broad brushes are correct. Best Rate Guarantees notwithstanding, you often won’t get the best price possible for a room by booking on the internet or calling a chain’s 800 number. A hotel’s in-house reservations or revenue manager can certainly often provide a better deal.
You usually won’t do better that way than on Priceline, contrary to what the article suggests, and the techniques involved are tedious and time-consuming… but there’s little downside, especially in just realizing that while some chains offer discounts to members of their loyalty programs, that’s not where to start when dealing directly with a hotel that sees the program as a tax rather than a benefit.
A better discussion of using corporate rates can be found on Flyertalk than is offered in the article, however.