Stand or sit with feet shoulder-width apart and core braced
Hold one dumbbell with both hands or use one dumbbell in one hand
Raise the weight overhead with arms fully extended
Keep elbows close to your head and pointed forward
Lower the weight behind your head by bending only at the elbows
Stop when your forearms are near parallel to the floor or as far as comfortable
Press the weight back up by straightening your elbows
Keep your upper arms still throughout the movement
Avoid arching your lower back
Repeat for the desired number of reps