exercise selection is one thing. if you include all the basic, compound lifts in your routine, that's good. if you do tricep-specific movements like close grip, that's good. incorporate a good mix of heavy pressing (lying down and OHP) movements, so that your triceps are forced to work under the greatest load possible. skullcrushers are popular too.
but, i'm more interested in the weight you're pushing. you can lift a good amount? great, but are your poundages going up consistently? if the weight you move keeps going up (even slowly), and your diet supplies you with more calories than you're burning, then eventually you'll grow.