Prague is such a beautiful city. It is rare to see a European city that has been completely untouched by war. There was so much history to learn about in Prague. I took a walking tour which I would recommend to someone going to visit. See the sights on foot - then decide what you want to come back to. The city itself is very cheap. They do not accept Euros so make sure you understand their currency (koruna) before you arrive. You can walk everywhere, stay in Prague 1 or 2.
Insider Tip:People eat early there. Make sure you sit down for dinner by 8pm - the latest (20:00h). Most of the nightlife is "underground" - find out where to go before hand. You will not just happen to stumble upon Prague's nightlife. The pub crawls are mostly younger college kids. :) Enjoy!