I'm sick of my thick, shaggy hair. What should I do with it?

Since I was in high school I've kept relatively the same hairstyle, the shaggy look. From time to time I cut it all off and let it grow back into the shag. Problem is, my hair is so thick and coarse, that it just ends up poofing out all over the place unless I tame it with a hat or beanie. I'm sick of this and need a change, although I'm unsure what to do. If anyone has any advice, it would be much appreciated.