First, remember no list is comprehensive. You have to use your brain. Look at the cues he or she gives you, and, if you know him or her well enough, you should be able to tell at least partly what he/she is thinking. Does
it add up?

• If he or she makes a point to be with you, even when he/she doesn't have
  to be.
• If she/he flirts with you, especially if you are the only
  person she/he flirts with.
• If he/she tries to impress you, going out of his/her way to help
  you.
• If she/he treats you better than other boys/girls.
• If he/she looks out for you.
• If she/he sticks up for you.
• If he's/she's there when you need him/her.
• If she/he makes statements like, "I wish you were my
  boyfriend/girlfriend."
• If he/she talks about how he'd/she'd treat you if you were his/her
  girlfriend/boyfriend.
• If she/he asks your friends questions about you.
• If your friend asks who he/she likes and he/she says he/she won't say
  because he/she might tell the person.
• If she/he calls you just to talk.
• If he/she jokes about being your $boyfriend.
• If she/he stares into your eyes but won't tell you why.
• If he/she smiles a lot around you.
• If you laugh a lot together.
• If she/he walks you to your classes.
• If you talk often.
• If he/she always seems to know where you are.
• If she/he touches you gently.
• If he/she gives you small presents or sends you cards (whether by
  mail or online).
• If she/he writes you often (notes or e-mail).
• If he/she gradually/suddenly becomes a lot sweeter.
• If you ask him or her to go somewhere he/she's not going and he/she goes just
  to go with you.

One warning: do NOT have your friends ask if he or she likes you.
This is the absolute worst thing you can do. First, it shows
you are a coward. NO ONE likes a coward. If you don't care enough
to ask the person yourself, you don't really care that much--
that's what he or she will think. Second, he/she won't tell your friends the
truth anyway. Save
yourself the trouble and ask on your own.

Hopefully now you have some idea whether he or she likes you or not,
although you might be confused if you're very close friends, and in
any case you're still probably wondering how to know if the person likes
you for sure. Well, you're in luck-- there is one surefire
way to tell if your crush likes you, and it works every time.