Overhead Barbell Tricep Extension:
Sit on the bench. Take a lighter weight for the first set. Hold the bar on straight arms above your head, grip should be narrower than the shoulders. Inhale and lower the bar by the head, bending your elbows. Exhale and return to the initial position. You can also use an EZ curl bar.
Exhale when you lift the bar and inhale when you lower it. Slow pace and smoothness of movements is the best work for your muscles.
Keep your back in the right position and choose a suitable weight.
Right weight for the barbell is when you can do the needed number of repetitions without violating the technique.