Chris and Chris:
There is nothing you can do to absolutely prevent theft and loss -- on the road or in "real life" back home. To me, the trick is to equip yourself so that if theft should occur, it would just be an annoyance and not a show stopper. This is what I do -- and you might want to pick and choose what works for you:
1. I never bring with me anything that I can't replace -- either financially or sentimentally.
2. I stay in decent hostels/hotels. No guarantees, but you can minimize chance of theft by avoiding the truly dodgy places.
3. My clothing and pack are all simple and inconspicuous. We travelers are always going to stick out -- but we don't have to make it any worse by wearing loud colors, funky styles, expensive brands, or using those ridiculous looking Pacsafe nettings, etc.
4. I spread my stash of money and cards as follows:
A. Wallet - driver's license, medical insurance card, 1 debit card, 1 credit card plus 3 days' worth of cash. I put my wallet inside a zippered pocket that's somewhat safe but still convenient.
B. Second stash -- I stash all important docs (passport, tickets), another 2-3 days' worth of cash plus 2nd credit card in a separate, more secure trouser pocket.
C. Third stash -- I stash some emergency cash (euro or dollar) plus a third credit card deep inside my backpack.
With the above, whether I get pickpocketed or lose my backpack -- I can still continue on with my travels. This helps to provide peace of mind so I can enjoy my travels and not subconsciously give off any bad vibes of fear or paranoia that thieves and robbers can sense a mile away.
Finally, it's a good idea to write down the account numbers and emergency contact numbers of your passport, cards, travel insurance, etc. DON'T write down everything (I leave out bank names and PIN's, for example, since I know what they are) and scramble the info. a bit so it won't look so obvious. You can print out a hardcopy and/or email the info. to yourself so you can access it wherever there is internet connection.
Hope this helps.