Notice her body language around you.
If you ever touch her, does she touch you back or kind of lean away? If you ever try to flirt with her, does she act happy or uncomfortable? When you guys talk, does she lean towards you? Or away?

Watch for clues that she is trying to avoid you. 

Do you ever see her wandering around in a hiding sort of way? She might just be trying to avoid you.

Notice if she smiles at you.

Sometimes when you talk to a girl who doesn't like you, she never smiles at your jokes or ever smiles at you.

Observe if she flirts with other guys.

She might not be interested in you if she flirts with other guys, but she might be trying to make you jealous so do not assume she doesn't like you!

Listen to what tone she talks to you with. 

She might seem in a hurry or she might not want to be around you. Sometimes she might just be grumpy or having a bad day.

Wait for her to strike up a conversation with you. 

If you're always the one to talk to her, then she might know you like her and she might never go looking for a conversation with you.

Does she ever ignore you? 

If she does she might not like talking to you. But, be careful, she might just be trying to act as if she doesn't like you.

Here's a test that never fails:
Pretend to drop something in the hallway. If she helps you she might like you. You two might even get into a conversation! But, be careful, don't get kindness mixed with likeness.

Notice her friends. 

Girls almost always tell their friends who they like. If her friends ever laugh at you or her, they might think it's funny that she likes you. They might act immaturely and tease you and her. If they don't do this, and they are either mean or normal around you, they are either good at keeping secrets, (which, when it comes to girls, they are probably not), or the girl doesn't like you. So, in this case, she probably doesn't like you.

Notice if she ever looks your way in class. 

Sometimes a girl who likes someone tries to look at him when no one's looking. If you catch her staring at you, she might like you. If she never even looks your way, she may be trying to hide the fact that she likes you, or, she may be really focused on her schoolwork, which probably means she doesn't have any feelings for you.

Do not just try, but do 

Adios
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