there are charts out there for selecting broadheads, but it also depends on your fletching and fps, going to a pro shop that really knows what they are doing is probably the best way to do it. Make sure you find a shop that will give what is right for you, even if it is the cheapest one there. I have learned that the more expensive new broadheads are not necessarily any better than the old standby. Once you get a broadhead style you like just play a little with the weights ntil you find what fits you best. I have played around a lot with broadhead styles going from 2 to 3 blade broadheads to various mechanical broadheads and finally came back to 2 blade fixed broadheads. Accuracy and not size is the key because if you hit a deer in the liver with a 1.5" mech. broadhead it will take much longer to die, if at all than a 1" broadhead through both lungs. Consistncy is the key and for my that is 100 gr. First Cut 2-blade fixed broadheads. You can narrow it down, but it eventually gets down to just some guess and check.