Here is a quick test sit on the ground, put your legs together(straight out) and draw your bow. Very important to have a target to aim at and nocked arrow, if you don't struggle to pull the weight you are good to go. This is a tough exercise but one that uses the muscle group to draw a bow with minimal movement, the stuff required when drawing while hunting. I agree with the others your comfort range is the best to determine what weight you set your bow at, if you can't pull/hold comfortably 70 lbs than don't.

FYI, bows perform best at close to peak wieght, so if you are only going to pull 60 lbs your are much better off buying a 60lbs limb vs a 70lbs, this is not to say one can't increase their draw weight with conditioning of the muscles.(if you plan to only shoot 60lbs than be realistic and buy the right limb for your application.)