I would like to grow my hair out, but I don't like how wild it gets. Any suggestions?

I like my hair short, or when it isn't short, collected. My friends all tell me I would look really good if I let it grow out, and I am inclined to agree, but I don't like my hair when it gets long. It doesn't grow down, it builds on the side. Soon it looks really stupid in my eyes, since I like to have a more refined look. What should I do? Is there any way to control my hair and still let it grow?