Hi MGZenMan,
There has been some great responses but I'd like to add my input as well. I very much agree with not talking Stranger Danger, a much more positive approach is Stranger Awareness, please see a blog bit.ly/1dZyx9A I wrote on the subject. Your child is unlikely to meet somebody who means them harm, so let's not scare them unnecessarily. Instead we need awareness and to make sure they know how to respond without thinking, you need to train them and refresh regularly.
You were looking for some structure to training, consider these steps to teach them:
1.Be aware of any people they don’t know, where are they, what are they doing
2.Keep a safe distance from strangers
3.If a stranger approaches make a clear (physical & verbal) signal that they do not want to talk to them
4.Make lots of noise and never give in if the stranger persists
5.Go to safety – Home, people they know who they are allowed to go to
6.Tell someone what has happened
There is an ever present threat of abduction by strangers, those people that say it's only friends or family that do bad things are wrong, the crime statistics don't back that up, please look at this blog bit.ly/1d1vDxp for the overview. Frightening, but luckily it's still small numbers, so much sure you teach your kids, don't scare them and refresh regularly.
I hope that helps, please check back on the blog for up-to-date help and advice.
Thanks
Gavin