Pointers-POINT me in the right direction :).

I feel that I'm being held back and would like to learn how to understand and use pointers. I think I need them to pass data from one instance to another. I've never used them before, but realize they are a powerfull tool. Are there any well commented tutorials?

Bascally I want a fumction to take an instance of an abject as a parameter and adjust a variable within that instance. I assume the answer is pointers.