Tricep Pushups: Get into the normal pushup position, but when you're bending your arms, the elbows come in parallel to the body instead of going out. Try 15-20 reps to start.
Tricep Dips: Sit on the floor with your hands shoulder width apart and your palms on the floor, fingers facing straight ahead. Bend your knees and lift your hips off of the floor. Bend your elbows, lowering your body to the floor and keeping your core engaged, then extend the arms to lift back up. Remember to keep the shoulders down!
Tricep Kickback with Lunge: Get into a deep lunge position, with your torso leaning slightly foward and your core engaged. Holding five-pound weights with your elbows pulled in to your sides, extend your forearms back until you feel the triceps squeezing.