If the theft is committed at work, it very much depends on there orders. For example, in the case of "passage dthief"when back and forth tossing and employees, and occasional visitors, the chances of finding the thief, alas, minimal.
You can set the camcorder (of course, disguise). The number of "dedicated" should be kept to a minimum to not know the thief himself, if he is from among the permanent employees – and this happens frequently.
Or to set a trap by using if accidentally left money or valuables, and "special offers", which when touched emit a jet of leave-in powdered paint. But there is a possibility that you will fall not a real thief, and "a" do not withstand the temptation people (the money is in the mind, like an orphan, and how not to use!).
You can also conduct your secret investigation. Very well, if a team is a former law enforcement officer: he can, using their previous experience, to "calculate" the thief. But again, there is the danger that the innocent suffer. Especially when you consider that the thief will try by all means to divert suspicion from himself.
As you can see, universal and absolute guaranteed methods no. So even if you are absolutely sure your colleagues do not leave money and valuables unattended, and when you leave the room, lock it.
As for pickpockets, among which come across the real virtuosos of their craft, they, alas, can only be caught red-handed on "the scene". Be careful and use the most basic vigilance. At least keep your money and documents in your back pocket! (It is not for nothing called "other").