If she looking at you just wait a second look at her if she turns arounds quickly that means she checking you out or if you say something she starts to laugh at your joke , when she say hi smile or whatever that mean she likes you
When she blushes when she sees you, smiles a lot to you, lowers her voice (like to watch her manners? like she doesnt wanna give a bad impression of herself, idk that's what I do :P ) and when she tries to find ways to talk to you get closer to you
<3 good luck! Actually you'll know it when you see the signs, it's just that some boys are just too oblivious to the fact that WE like em. Open up yo eyes yeah!
Does she talk to you a lot recently? Does she smile to you a lot? Is she shy when you look at her directly? Try to ask her who's the guy she likes. If she says no one and glances shyly at you, if she changes the subject of the conversation, yes, she like you. Answer from a guy who has rich dating experience and especially online dating, having dated girls from eHarmony, Match.com and IDateAsia.com.