My wife and I watched a group of pickpockets stalking their victims in Prague. The overcoats were a giveaway.
Best strategy I know is to have a zippered pouch sewn into the lining of your slacks, hanging from the waist. Carry a bit of walking around money in your pocket, and your credit cards, cash stash and other valuables in the zippered pouch.
I usually leave my passport in the hotel room safe if they have one. You don't need the hassle of replacing a passport overseas. (just in case, scan the bio pages of your passport other critical documents and email the scans to your gmail account to ease the process of replacing a passport)
The pouches that go around your neck on a string under your shirt are also good. Get them at any travel store.
Enjoy, Prague is a great city.