What do you when you have a crush?

Since when I was young I never understand the step of having a crush on someone. So you like a person without telling them then you got their number and start talking to them but it always seem to be creepy, awkward and ended up never work out, So now I'm in college I still don't know what to do when I have a crush on someone. There's a guy in my class who I have my eyes on, I finally got to hung out with him at school which toke awhile but the semester almost over and I still don't even have his number. I don't know how to ask without being awkward or too obvious since I kinda know nothing about him other than we have a class together.