'Chirpsing'

Hey loyal prosperous friends from other lands! hope everyone's had a fab January and are ready for the other 11 months of the year!
So chirpsing also known as flirting is by definition is 'To chat up, flirt with, a memeber of the opposite sex' thanks to urbandictionary.com for that fine definition of this mystery language. But my problem is where is the line between a friendly chat and flirting? The line so fine I can't even see it.. and there are two issues with this 1. How do I know what's appropriate to say? 2. How do I know what they mean by what they say/ what their intention is?   
I really can't help anyone else in this situation because to be quite honest I don't know the cure myself.. So in case you couldn't tell, I am in fact, deep in this situation. And being one of the unfotunate sufferers of social awkwardness (and by that I mean i'm actually too confident and i don't know when to stop talking) this is particularly challenging for me. So what do I do?? well I pretend I don't know what he's trying to say and so I try and resume casual conversation.
GOOD LUCK TO ALL YOU CHIRPSY LITTLE BLUEBIRDS
Underaverage Girl
xxx