Safety is a majour issue for me. I'm from SA... last time I checked, our crime levels were among the highest in the world. Statistically, she has 1 in 4 chance of being raped before she is 18. I find that absolutely terrifying.
Here are some of the things I do:
First, I keep her safe as much as possible - she is not to leave the yard without me, or open the gate, or even less so the door to anyone. When we walk in public, she holds my hand, unless it is very quiet, in which case she may walk in front of me. I have to always be able to at least see her.
She doesn't go to anyone's house without me, unless I know the family well. I'd much rather invite kids over to my place, with one or both parents if they want, than to let her go to someone I don't know.
My daughter has a bracelet with her name, my name and my cell number on it. The rule is that if we are in public and she can't find me, she is go to anything that looks like a desk - a cashier, information, whatever, and ask them to call me. Thank goodness, this has never been necessary.
She will be getting her first cellphone for her 6th birthday in October. Yes, go ahead and tell me she is too young and in how much trouble it will get her. I don't care. I'm getting a package that will allow me to specify the numbers she can contact and that can contact her - me, my brother, my SIL, my GF, her best friend's mom. That's it. No friends yet - that will come when she is significantly older. It will go into her bag, switched off, and she is to use it whenever she finds herself in any situation that she doesn't know how to handle, or that makes her uncomfortable. For me that is a safety issue - my daughter must be able to reach me if she needs help.
I try to empower her, by teaching her how to handle various situations, and letting her handle as much as she is able to (of course, with supervision when required). This range from something as small as finding her own way from the school entrance to her classroom, to bigger things, such as knowing what she can do if she can't find me in a public place. We often play the "what-if" game - I give her a scenario, and she tells me how she would handle it, and then we discuss it if necessary.
Like bssage have taught his kid, I have also taught her that she need not allow anyone to do anything that makes her feel uncomfortable. And when she gets uneasy, she is allowed to get herself to a safe place by whatever means necessary. I have never, I will never tell her to trust anyone. She's allowed to make up her own mind. And like bssage, I have taught her that I can defend myself - she need never feel responsible for my safety. (I may have hinted at something bordering on super-powers).
The bathing-costume rule - no one is allowed to touch her in areas that is covered by her bathing costume. Also, she is not required to touch anyone anywhere they tell her to.
As soon as she is old enough, I will also enroll her in self-defense classes. For those times when I'm not there to keep her safe.