How do you know a girl finds you attractive?

Like physical attraction, etc

Girls feel free to answer lol

There's no definitive sign... but generally some of the following are good indicators:-

1) Her smiling at you lots whenever she sees you; also if she makes a point of actually talking to you when she see you (i.e. never a quick "Hi"
2) Her going out of her way to talk to you, or get your advice / opinion (esp if there are better people around)
3) Her behaving differently towards you than others without an obvious trigger (note this can also include her being moody / stroppy with you for no apparent reason).
4) Complimenting you on something you're particularly good at
5) Laughing profusely at your really bad jokes (unless it's completely un-PC, of course)
6) You coming up in conversations with her friends (hard to find out, but sometime girl-mates give it away)
7) You just happen to mention a particular thing you like about girls, (e.g. clothing, hair / make-up etc) and guess what she's sporting the next time you see her?
8) Random looks/ stares/ gazes over in your direction.
9) She stalks you on social media (and likes A LOT of your content).
10) She says "Yes" when you ask her to go for a drink or something :wink:

As I said, none of them are definitive signs, (well maybe apart from the last one lol), so it's best to look for a few indicators rather than just relying on one or two. Also, bear in mind, it's a lot harder to read a shy or reserved girl.