When to add a girl on FB?

So I met a few girls today at a meetup. We did a few activities together and talked a bit but that was it. We'll see each other again at the next event. My question is, if I like this girl, should I add her on FB now or wait until I get to know her more before adding her? Thoughts please?

DO NOT DO IT NOW!

Mate, you have to think REALLY hard about this! When it comes to girl's WHO FREAKING KNOWS how it would go down when it comes to adding them this early! DO NOT TAKE THAT CHANCE, SOLDIER!!!

I HEAVILY ADVISE A MINIMUM TERM OF 4 WEEKS FOR FRIENDSHIP BEFORE YOU ADD HER. BUT DO NOT GO OVER 6 WEEKS OTHERWISE YOU ARE WITHIN THE FRIENDZONE!! IT IS IMPOSSIBLE TO ESCAPE THE FRIENDZONE AND A SIMPLE "ADD TO FRIENDS" WILL BE MEANINGLESS TO HER!!!! WITHIN THOSE TWO WEEKS, YOU MUST ADD HER, TAKE HER TO DINNER, GET TO KNOW HER BEYOND THE FRIENDSHIP POINT, AND BEFORE YOU KNOW IT YOU GUYS ARE LIVING HAPPILY EVER AFTER!!

DO NOT RISK IT!!!