Passing parameters between methods.

My team is programming a game of tic-tac-toe. To keep track of X/Y turns we are using a parameter named counter. We can pass counter forward from the control method along to as many called methods as we want. The problem is that when we increment counter within a method (counter=counter+1) the returned value that we get in the method is not being passed back out to the control method. How do you pass these parameters back and forth properly?

I appreciate you time.