This will give you an idea of what to do (go to bottom of page):
Once you know your current balance, you can use this to modify and use your balance board to verify & refine:
All you are doing is trying to find out is where your racquet balances (doesn't flop over one way or the other). Then you take that point measured from the butt, and compare it with a reference point on your board ... that is what the ruler markings on your board are for. Depending on whether your racquet is 27", 27.25", 27.5" long, your reference point on the board is different. Your reference points are 27/2, 27.25/2, and 27.5/2. If your balance point lines up exactly with the reference point, then you have neutral balance (zero points). If your balance point is off to the side of the reference, then you have either head light of head heavy balance. The difference between the balance point and your reference point is your balance. In Europe, people talk about balance in terms of millimeters. In the US, balance is expressed in terms of "points" ... a point being 1/8".