What's the difference between shiny hair and greasy hair?
One is when you don't give a dam, the other is when you haven't washed your hair and are trying to hide the fact you haven't.
Best thing you can do for you hair is just to wash it in water. Shampoo and conditioners wash out a lot of the natural protective oils in your hair and then try and replace them with artificial ones.
If you wash it too much it will start to fall out in big clumps (happened to a friend of mine who was told to leave her hair for a couple of weeks so it could sort itself out).