Try not to wash your hair everyday, try every second day. When your hair is use to getting washed everyday, it gets greasy easier. For the days you don't wash use dry shampoo. It is a spray that takes the grease out of your hair, you can get it anywhere hair care products are.
Don't just wash it in the shower, scrub it. With your fingernails and scrub for like 2-3 min, and rinse super well. When you dry, put the towell on your head and dry it off as if you were scrubbing in more soap, if you know what I mean.. If you don't then just do the first two steps and dry as you normally do.