When teaching your children, modeling behaviour is the biggest way to set expectations. I can think of one time I watched a very young mom hanging out at a gas station picking up smokes scold her daughter who had a ciggie on her lips. You don't want your kids to smoke, don't smoke. Learning who to talk to, and how to stay safe is a LOT harder unfortunately, but you can model the behaviour of who you talk to and tell her why.
The fact is 90% of molestations/abductions are perpetrated by a 'known' relative, friend, or other person of trust. So just teaching your child to "not talk to strangers" is misleading and can be more dangerous than not talking to her about bad people at all.
You need to frame your discussion around keeping herself safe in ALL situations. IE, no one looks/touches/photographs your private parts. Except a Dr or mommy, and then it's only to keep you healthy when there is problem.
When you're out, do you talk to strangers? Yes, everyday. The bank teller, the cashier at the grocery, the random person at the park. You need to teach your daughter WHY you talk to certain people, and not others. Who to go for help, and who not to approach. EX, saying a
police officer' doesn't cut it. When was the last time you saw a police officer wandering around a park? I never have. However, there are lots of mommies, and mommies are usually safe if you're in trouble. What is 'in trouble', when you can't find mom, if someone comes up and starts a conversation with you, asks you to help them (do normal adults ask kids for help? no, it's a warning flag) etc.
When in a store, an employee will have a uniform of some sort, and a cash register is always located at the front of the store. That sort of thing.
I'd recommend you read "Protecting the Gift" by Gavin De Becker.And Feather Berkower has an EXCELLENT workshop on Parenting Safe Children here in CO. http://www.parentingsafechildren.com/
And remember, this isn't a one time deal, there are 'teachable moments' throughout the day, it's an ongoing discussion. GL!