Many exchange places in Prague won't just rip you off, they will skin you alive! I highly recommend going to YouTube and searching "Honest Prague Guide Change Money"

Janek Rubeš deserves a medal for the work he is doing! As a matter of fact, watch all of the Honest Guide videos you can before you go.

Most places in Prague take credit cards and many accept Euros (often at better rate than exchange offices), so you won't need a lot of crowns unless you plan on travelling outside of "tourist" Prague.

Cabbies are also notorious scammers in Prague, too! Metro and trams can get you almost everywhere you need to go in the city, even from the airport to downtown. Best part is, the price, a 24 ticket (unlimited rides on metro, trams, buses, ferry and funicular) is 110Kč which is about $4.88