You might also consider a small backpack as a dummy. When I was in Paris, I was hyper aware because we had been warned about the pick pockets, etc. A common place is in subway stations, especially on the stairs. A lot of times they are crowded and people aren't paying close attention. But I had my backpack with snacks, a guide book, and a notebook in it. Nothing valuable went into the backpack. I kept my money in a bag in front of me. Anyway, we entered a subway station and it wasn't busy at all. It was just my husband and me, and these two guys behind us. The stairway was really wide....it's built for crowds of people, so several can go up and down all at the same time. I found it really strange that in a basically empty stairway, these 2 young guys stayed right behind us, especially since it seemed like they were hurrying to get down onto the platform. They were several yards behind us, hurrying down and then suddenly they were right behind me. It just didn't feel right to me. Then I felt my bag jostle just a bit, like someone had tried to open it. I turned around and the guys took off. I took the backpack off and the front compartment was halfway open, with the notebook sticking out. So they were definitely pickpockets, but there was nothing for them to pick, and since I was paying close attention, they didn't have a chance to even get that. All they would have gotten was my notebook, but still.
There are also backpacks with hidden compartments for wallet and passport that go against your back so a pickpocket can't access the pocket unless it's not on your back. I think just being aware of your surroundings is huge. Learn to say "No thank you" in whatever the local language is. If someone approaches you, just say no, thank you and walk away. They most likely aren't going to chase you. Just don't allow them to distract you. And be wary of street performers...often they work in groups, so one or two will be doing some performance and others walk through the crowd of spectators to pick pockets. If you do stop to watch a performer, make sure your valuables are not in an accessible place. Where are you heading, again?