2 ways to go if you're looking into prague:
1) The "strip" clubs, the best of which is K5 since they speak very good english and are very accomodating and have some fantastic looking girls. I actually did a review (Alina) of one of the girls i saw and it was very reasonable (US$100 or so for an hour). I highly recommend K5 above all the other clubs, but you might want to make a reservation, as they are pretty busy. Just take a cab there and don't let them convince you to go anywhere else.
2) www.escort.cz   : They have tons of listings for agencies and privats that have awesome looking girls and the prices are great too. The only problem is that you don't know EXACTLY what you're getting since you communicate by phone or email. I met one really gorgeous girl who was into EVERYTHING and was only $200/nt (which supposedly was exensive, but i didnt care much and even tipped an extra 50 since it was my last night).

DO NOT go with any of the street girls/gypsy girls as they can be extremely hazardous to your health. They'll quote you a ridicoulously low price just to get you to come with them. Don't do it!
Above all, have fun!

*This was as of 2 years ago, so take it with a grain of salt. I hear they're not really too fond of americans these days.*