Male - 27 Years Old
ok you're getting advice from losers, so i'll help you out.
If a girl likes you enough physically, you don't have to say much to get her to like you. I've had a girl walk up to me and say "you're really pretty." I nodded, smiled, and gave her a hug and kept talking to my friend. we ended up going home together.
That actually happens a lot but not all girls are hot enough.
Guys should never go talk to some girl they like without knowing if she's a little interested. I've never walked into somewhere and just said "i like that girl i'm going for it" without her giving me some sort of signal. there's too much room for rejection: she's just there to be a DD, she has a bf, she's not dtf, whatever the case get confirmation first.
If a girl talked to you in class odds are she likes you. but first impressions are key. by the time i was a senior i knew how to make a very amazing first impression. if she's in your class easiest thing to say is "lets study together at my place". I had a girl show up without her books ( that was f*cking awesome)
I had a next girl tell me to come to her place at 8pm. she opened the door in a towel as if she just got out of the shower. no studying got done.
on the off chance studying does get done, study until late at night until it's too late for her to go home. i had to do that on finals week. she showered in my shower, wore my clothes, and then sat on my d*ck.
i can go on, but since you're 20 i assume you're in college so that's all you really need in college, the patented "lets study later"