You're at increased risk when you are away from your normal living area. 

Money
Don't pull out a wad of cash when you are ready to pay.  Here's a great trick - as long as you have pockets.  Separate your bills by denomination -- small bills ($1, $5), then larger ones.  Fold each bill in half, with the folded side up, and take the groups of folded bills and slip them in your pockets.  Use a front pocket that is otherwise empty for your smaller bills (the ones you'll be using most frequently), and a back pocket for the larger ones.  Then, when you need to pay for something, slip your hand inside the appropriate pocket.  You'll feel the folded edges of the bills and you can pull out one or two, as appropriate.  This also works great with foreign currency.  Anyone watching you will be unable to tell how much money you have.

Credit Cards
Pickpockets and other criminals would love to get their hands on your credit cards.  Be aware of this, and follow some simple credit card security guidelines.  First, only give your credit card to a reputable business -- never to a street vendor.  Keep all of your receipts until your credit card statement has cleared, and check for altered amounts and inflated charges.  You should have at least two credit cards with you on trips.  Keep one of them in your front pocket (with those small bills - see above), and one of them in a more secure place (see passports below).

One additional word on credit card security.  We gave a very well known national credit card to a London cab driver for a taxi ride to the airport.  He forged a second credit card receipt for over $1,000.  The credit card company initially refused to take the charge off our bill, even though the signature did not match, and the charge was made at a time when we could prove that our return flight to the U.S. was already in the air.  As much as we dislike carrying a lot of cash, using local currency does eliminate any fraud issues.  Yes, we finally got the charge removed from our bill, but it took a letter to the president of the credit card company and numerous phone calls to accomplish it. 

Passports
Our best tip - keep them out of sight.  We use zip up pockets that have a loop for a belt.  You thread your belt through the pocket's loop, flip the pocket into the side of your pants, and it is invisible.  There is plenty of room for backup credit cards and extra money.

Cameras, Laptops, Jewelry, Watches
Every year, many of these items are stolen by unscrupulous hotel employees who visit your room while you are away from it.  Don't leave these items out for them.  If you don't have a safe in your room, or the item(s) will not fit in the room's safe, store them in a safety deposit box at the front desk. It's a little bit of a hassle, but it will be much more of a hassle to replace your stolen property.  (And don't even think of hiding it in your room -- "they" know the common hiding places.)