I've been to Amsterdam at least 10 times. My favorite hotel is the Sofitel Amsterdam, about a 5 minute walk from Centraal Station if you're coming by train, ferry or the Schipol airport train. Very convenient to everything. The Red Light District is a few blocks away, but far enough that it's not noisy or dodgy.
Other hotels I've stayed at the NH Barbizan next to the train station (If you've got the cash, splurge and stay here!), the Victoria (ok, used to be nicer), a few of the Tulip hotels and the Ramada (Small rooms but great value).
For a great cheap meal, try Chinatown, not far from the train station. You can't go wrong at any of the little family-run restaurants!