Ive been to prague 3 time. Cheap beer, a lot of attractive woman, very cool city to walk around, lots of casinos and strip clubs. Make sure you get a chance to walk charles bridge its a pretty sweet view/experience and head over to prague castle for an even better view.
Also keep your wallet in your front pocket and do not have it visable. Also do not spit, locals take it for a sign that you want to fight.
If you take a cab, make sure your cab driver agrees or quotes you on the fare (negotiable) before you get in the cab.
Airport is a good distance from Prague so most take the airport shuttle. Cab/limo ride is much more.
Some or many places do not take credit cards, cash only. Be sure to confirm before you sit down for a meal. Hotel food is usually not recommended. Go where the locals go. If its crowded, its probably good.
Not sure what it's like in winter but the St. Charles Bridge is cool to wander around on. Very touristy, yes, but there are some pretty neat things you'll run into. We saw a guy with a mechanical marionette that was dancing around to music. Just really cool. You can get some nice artwork too. I got a beautiful painting of one of the cathedrals in the area (don't recall which one).
Prague is awesome. Would go back anytime. We also spent a few days in a small village about an hour away called Trebic. Equally beautiful. Would recommend.