Pickpocketing and other crime
Oops, you thought this would be a pickpocketing tutorial! Sorry to disappoint you!
First of all, I want to explain that Paris is generally an extremely safe city. I've lived here off and on since 2005 and have never had a single problem with pickpocketing, and neither have any of my friends in Paris. I absolutely do not want to make anybody paranoid during their visit to Paris! But it's better to have good habits and be wary of crime rather than be oblivious and get victimized; I can barely imagine the grief and hassle of losing one's passport or money during a vacation in another country. So please do read the following, set up a good safe routine for yourself in order to not be vulnerable to pickpockets, and then forget all about it and enjoy Paris!
One thing I've figured out is that most Americans (like me) aren't really conscious of pickpocketing at all, and I think it's safe to say this is because pickpocketing is much more rare in the States than in Europe. My personal theory about this is that in America it's very easy for criminals to get guns, whereas in Europe it's much more difficult. So in America if you want somebody's money, you choose someone in a dark secluded place, show them your gun, and ask for their money! Easy! I've personally known half a dozen people in my hometown of Philadephia who were robbed at gunpoint, and I've never heard of this happening to anybody in Paris, neither friends nor strangers. So, since robbery at gunpoint isn't an option in Europe, thieves have to be much more crafty. This is, in my opinion, a main reason that the art of pickpocketing is still going strong in Europe, and it's also part of the reason why Americans are relatively easy victims: A) We aren't used to thinking about pickpocketing because it's not a big problem back home, B) we're used to feeling wary of crime while in dark places when no one's around, but completely at ease in big crowds, especially during the daytime, and this situation is completely reversed with regards to pickpockets, who rely on large crowds, and C) just being foreign our clothes, our language, etc. makes us stand out a bit as potential targets to pickpockets. We tourists are overwhelmed with the sights and sounds around us and are less likely to notice a hand in a pocket than would be a local guy on his way to work.
So, how to protect yourself? There's absolutely no use walking around Paris or any city and trying to look out for who might be a pickpocket. The best defense is extremely easy: simply never have anything of value in your exposed pockets. Keep your money, passport, and credit cards in an inside jacket pocket, or better yet, one of those necklaces with a pocket that you can wear under your clothes.
Women should always keep their purses or handbags closed, with the flap or zipper in front of them, never behind. In a crowd, it's very easy for a thief to open your bag and reach inside if it's hanging behind you. Train yourself to hold onto your bag tightly! It's very easy for someone in a crowd to snatch your bag from behind and run away.
Places to be especially wary: in tight crowds in train stations, on crowded Métro platforms, in the Métro itself, on crowded escalators, and any crowded places like outdoor tourist attractions, shopping areas, etc. Notice that the key word here is crowded. When you're in an open place without a lot of people, you'd definitely notice someone standing/walking directly behind you and or touching you, so thieves know not to try it in places like these. In big crowds, we quickly get used to the proximity of lots of strangers, and we stop noticing the occasional bumping of shoulders and pushing and shoving, and all of this makes for a perfect cover for theft.
Some other tips about crime
Never put anything down; your bag, your camera, your wallet, etc. If you put down your bag for even five seconds, it's very easy for someone to run by and grab it. I've been approached a couple times by young kids around the Les Halles area who want to sell me a digital camera with no case, and it's obvious they just snatched it from a tourist a minute earlier.
When you're on the Métro, don't put your bags underneath your seat. It's possible for thieves to sit behind you, reach under the seat, and try to slide your bags away from you. This happened to my old roommate once, but she noticed, grabbed onto her bag, and the thief stopped and quickly slipped away.
Be mindful while using your smartphone if you're in a crowded place, as thieves will sometimes run up from behind someone and snatch the phone right out of their hand and keep on running. This happened to an acquaintance of mine right after leaving my apartment in Montmartre/Pigalle.
Speaking of Pigalle (aka the red light district), I would say that's definitely one of the neighborhoods where you're most likely to encounter pickpockets, with Les Halles as the other most likely. I love Pigalle myself, and I once lived there for a year and never had any problems, but I did witness a tourist getting her purse snatched away from her right at Place Pigalle on a sunny afternoon with tons of people everywhere. I should mention that's the one and only time I've actually seen anyone being victimized by thieves in all my time here. Anyway, the vast majority of the time, Pigalle and every other part of Paris is very safe!
While I'm at it, here are a few more articles I've written about other minor scams and cons in Paris:
Okay, enough warnings! Keep these tips in mind, and don't worry! It's very unlikely that you'll have any problems at all, especially if you protect yourself with these simple habits. Set up your routine and arrange your valuables on your person in such a way so that you're not vulnerable to thieves, and you can forget all about it!
(And, uh, if you do find a good tutorial for pickpocketing, please let me know!)