I've met online friends in real life twice. Both initial meetings were at public places and one of those meetings has turned into an enduring RL friendship where we go to a con together every year and celebrate the 4th of July together. My wife has met some online friends as well and it's worked out pretty good. The 'in public' first rule would have to be the standard-bearer, but I can certainly testify that meeting people can be worth it!
~Aldin
~Aldin