If a woman is interested in you, she will let you know by giving you signs-
IOI's (Indicators of Interest) so be on the lookout for the following:

-Eye Contact/Extended Gaze: If she is looking at you from a distance, she's interested if she maintains eye contact with you for 3 solid seconds or more.. so feel free to approach her.. say something like "I saw you looking at me/staring at me.. (thought I'd come over and say hey, introduce myself...) or (you kept looking at me so I take it you like what see..)
-If she is close to you and maintains good eye contact with you, she's interested in you or at least what your saying... If she's doing the triangle technique, where she's looking at one eye, then to your other eye & then to your lips, she's definitely interested in you and is probably thinking about kissing you/what it would be like to kiss you.

-Smiling- Especially if she's not particularly "cheesing" at you, but doing the more seductive half smile/smiling at you with her lips closed, and tilting her head slightly down and/or looking away after she smiles at you.. only look back at you again shortly after.

-Flipping/Touching/Twirling Her Hair with Her Fingers- Flipping/touching her hair is a good IOI. When a female actually engages in convo with someone they're interested in, she'll continually touch her hair. No matter how short or long, she'll usually find some way to flip, twist, brush or run her fingers through her hair.

-Playful Touches- If a girl's interested in you, she will most always find some way to touch you, whether it's tapping you, hitting you, or poking you.

-Picking on You/Being Mean- Yes, if she is picking on you, she's flirting with you. Guys do the same thing. Use it to your advantage by saying something like "I see how you wanna be" and walk off and let her chase YOU or apologize to you.

The Cross & Lean- (This can only be done if she is sitting) If a girl is interested in you, she will cross her legs towards you and slightly lean in towards you to show she's attracted to you.. if she does this... it's a sign you're good to go

-Name Calling- If a girl is into you, you will notice she will say your name more often than your best friend... This is a more subtle cue, but something to get your attention.. like "Tripp, come here," or "Tripp, you crack me up" followed by a smile.