I'm currently living in Amboise as an english assistant and so have visited Tours several times. My main warning is regarding a night club called Wake Up! Now it is free to get in which is brilliant; however if you do go be extra viligant about bags, purses, phones etc. My purse was stolen from there and when I reported to the police he said it was a common occurence at this particular club.
Yesterday I was in the train station and was approached by two men who asked me for money. I decided to say I didn't understand the first man, however he was persistant and took a while to leave me alone. Almost straight after the second man came up to me and I spoke 2 words of bad french in an attempt to get him to leave. Even after ignoring him he proceded to poke me until he mimed what he wanted. I said no again and he left. I later saw the, talking to each other which made me think they possibly were working together. They seemed to just be approaching people using the ticket machines, but they later moved on to people sat at benches. I have never experienced that before so hopefully it was a one off cos Tours is a lovely city.
I may be totally off base but I was first directed to an internet place in Tours that just really gave me a bad vibe. I don't even know that it had a specific name but I remember very specifically where it is. At the northwest corner of Avenue de Grammont and Boulevard Thiers. As you're walking down from Place Jean-Juares, it would be on the right side of the road. I went in and was directed to a small, dark room that had just one small lamp and two computers. After I was there for about fifteen minutes one of the guys came in and shut the door behind him and tried to talk to me. But he spoke almost no English and I speak almost no French...but the bottom line is it all just felt a little off. Then he left and I very quickly finished only what I absolutely needed to do and then went out to pay. According to the tariffs listing on the wall and to the best of my ability to understand him, he was saying that I owed 2.50, but when I offered that to him in coins he shook his head and he and the other three guys that were just sitting there starting laughing. So I (with a kind of sick feeling in my stomach) thought maybe he wants paper money...so I gave him a 5 euro bill and it was like he wasn't going to give me change! Well, I just stood there and finally he, with a disgruntled manner, gave me a 2 euro coin back and I got out of there...no way was I sticking around for 50 cents. So perhaps it's an over-reaction...but I would just recommend that you try a different place...like CyberGate (see my off the beaten path tip)
not a real warning, but just be aware that many of the historical buildings, cathedrals and castles in France can be under renovations and construction at any time. Because they're so old, they need maintenance continuously!