How can I keep my hair straight and neat?

I have very fine, sleek, and thin long hair, and it gets knotted very easily. Is there anyway that couldn't happen? I would like it to be like that until the end of the day at school, but if its hairspray i don't want it so my hair looks soaking wet by the time i'm doing spraying it. I also want to try to find a way to keep it in place all day, so by the end of the day it isn't out of shape or anything, but the only problem is I have to put my hair in a ponytail for P.E , so anything that could withstand that too? thank you :).