What should i do when i see him again?

There was this guy in school(last year).He was sooo cute.When i saw him down the hall i can't stop smileing?I simie all the time,but this is bigger.Much bigger.When i saw him at lunch my hands keep sweating.I had a big crush. what should I do if it happens when i look at someone eles?I would die if someone gave me a handshake.