in my experience every site is different as every hotel is different. some make it cheaper the earlier in advance you book others dont. find the hotel you like then type it into google and all the websites it advertises on will come up. you can then shop between them to find the best deal. alternatively just google on the area you want to stay in. most of these websites charge a fee or advertising cost so sometimes you can get the best rate by calling the hotel directly. if you want to go that day would always recommend a direct phone call.
Does anyone know the timing process of how these sites work? Do hotels release cheaper rates at a given time on the day they need filling?, say, noon, if it s looks like they're not going to be full that evening?