(1) Buy a trigger pull gauge. (2) If you're satisfied with the trigger as it is, don't change it. (3) If it seems too heavy, take it to a qualified gunsmith.
My hunting rifles have triggers weights between 2 1/2 and 3 pounds, which is on the light end for factory triggers. Benchrest rifles have triggers measured in ounces, but they're generally not safe for field use while hunting. The other factor besides weight is "creep": how much the trigger moves before it fires. No creep is what you want.