1) Acting like you don’t care what happens- If you actually like a girl you need to let her know. That’s not to say you should be up her ass or blow her phone up, but talk to her, tell her how you feel, and show her that she matters.

2) Neglecting to recognize when you’ve done/said something to up set her- This is a problem with a lot of guys, mostly because the way females show they are up set with you varies from female to female, so I will break it down for you a little.
-If she usually texts you frequently and now she doesn’t and is short when she responds to your texts; she is mad at you, figure out and fix the problem at all costs or you WILL lose her.