How do I fix greasy,wavy hair?

I'm 17 and I'm a guy if it matters.I like my hair long.about inch below my neck in the back.Every day my hair goes totally out of control.It doesn't matter what shampoo I use, It always ends up knotty,messy,and greasy.How do I control it and keep it clean enough so I can actually be proud of it.I like the sorta skate-punkish look,Kinda like ashton kutcher's on that 70's show(but ashton kutcher is a tool so I don't like to compare it to him).

How do I fix greasy,wavy hair?

check the links below for natural homemade beauty tips to:-- Dry hair / Oily hair/ Splitends / Fruit Packs for scalp

http://geebal.blogspot.com/2006/08/natur...