1. Dips. It is important to remember when doing dips that you don't lean too far forward as this will recruit more of your pectoral muscles. You must try to stay as straight as possible in order to recruit your triceps.
2. Wide grip press downs. This movement is performed using a cable bar and pressing straight down. It is important to remember to keep your elbows fixed and parallel to your body. You must keep a wide grip this will help to engage the outer head of the triceps.
3. Dumbbell kickbacks. This movement is performed by taking a dumbbell and extending your arm. You can do it one hand at a time in a leaning position or double over the head.
Every exercise is performed between the 8-12 rep range and at 3-4 sets. Give these a shot or try implementing them into your program. You will not be disappointed.