It’s going to be an inexact process at best; it’s not as though grinding in bars gives you 120 XP per hour that culminates with your hitting the cap as a level 80 Pick-Up Artist.
Approaching people you don’t know and have no connection to means that you have to behave accordingly.
Tracking them down on social media, randomly texting them (when they didn’t give you their number) or proclaiming your undying devotion for them when you don’t actually know each other are all examples of assuming excess levels of intimacy.
The first message was relatively innocuous, but the ones that followed became weren’t – he was making the kind of jokes-but-not-really that assume a greater level of familiarity between the two than actually existed.
Two people who had at least a passing relationship online might get away with tweets like “For my birthday, I want @gracespelman to follow me back”; from a complete stranger, that’s just unsettlingly creepy.
A close friend might get away with an impromptu hug or a playful ass-grab; an acquaintance or total stranger who tries to pull the same move would get a surprise visit from the Slap Fairy.