I know this might not be feasible for many, but, sometimes before I travel, I'll get a new pair of trousers, take them to a tailor and have a couple of secret and securable, zip pockets sown in. Costs a little more, but they are unsightly and pickpockets don't know what to do with them.

You don't have to go to that extreme though. Thieves always gravitate towards the easiest targets, whether that's car in a parking lot or a person on public transportation.

So, not looking like an easy mark and just being more difficult to pickpocket than the people around you is usually enough.