Calves or thighs? Thighs are easy... Squat and/or leg press. Calves are another story. You can do stance training, calf raises, seated calf raises, etc but genetics winds up playing a huge role. The calf muscle can vary tremendously in where it sits on the leg, i.e. Mid to lower calf all the way to just below the knee level and it gets activated in different ways based on your leg structure.