Use common sense. You are no more likely to be harassed, raped or murdered on a photo shoot than in everyday life.
If you are unsure about the photographer, check out his references (contact other models he has worked with). If, after that, you are still unsure, don't work with him or her.
Make sure you tell someone where you are going, who you will be with, and when you expect to be done. If the shoot runs longer than planned, call them and let them know you are OK.
I would say that if you feel the need to be chaperoned, you are welcome to, but don't be paranoid about it. Do some background checks on the photographer instead. In my experience, chaperoned models can be inhibited, too self-conscious and are often unable to open their soul to the camera.
On the other hand, on location, a chaperone with the right attitude can sometimes be useful (carrying equipment, holding lights, etc.).
Never bring your partner, lover, boyfriend or girlfriend as a chaperone, they are always a problem. Have them in the next room, but not where they will be a distraction. It is very likely poison for your relationship with them and it may well inhibit the photographer.
There is one very important exception, though: If you are under-age, you must always be accompanied by an appropriate adult (e.g. a parent or manager, who is authorized by your parents).
If you are worried about safety on a planned shoot with me, I can put you in touch with models with whom I have worked in the past.
If you want to phone a friend to say that you have arrived safely, you are welcome to do so. During the shoot, however, I prefer mobile phones to stay switched off. I will grant you the same courtesy.
