From experience, which online site has the cheapest rates in regards to flights and hotels?
These days they're all about the same. I, often, use bookingbuddy.com as a research tool. A lot of the time you can find a flight on that site and then go to the airline's site and get the same flight for cheaper. This isn't always the case but I've done it many times. Places like expedia do add their own fees to pay their overhead so you can get cheaper through the airline or hotel. As the recession has lingered this has been the case less and less often but you should always check. Especially with hotels. Their website may have some sort of special that is better than what the online broker shows.
Priceline/hotwire is great if you don't care where you stay or what time you fly. If you have a specific hotel that you need for whatever reason than priceline is not for you. But, if you only wish to stay in a general area then use priceline. I got a Marriot in DC the weekend before Christmas for $75/night through priceline last year.
I've never used priceline/hotwire for flights because it's harder to control your itinerary. They choose what time you fly. If you don't care then use priceline. Personally, I take the train to and from the airport and am at the mercy of train schedules. I can't have a flight that leaves before the first train or lands after the last. If you don't have a stipulation like that then go ahead and try priceline.
ETA: All of the airlines except for JetBlue and Southwest charge to check bags now. That needs to be factored into your ticket price.
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