It's harder to get definition in the triceps, because that's an area in the upper body (of women at least) that tends to hold on to more fat. Aside from reducing your body fat through your diet and cardio, which would give more definition to the area, I find that lying tricep extentions are very effective for the area. I also like cross-body tricep extentions.
I've had good results with PUB, substituting lying tricep extentions for the tricep kickbacks. I also like that PUB puts tricep exercises before biceps, because I like to do them in that order (in order to have a bit more energy while doing triceps).
Other ways to focus on triceps: on some days, do tricep work first, after your warm-up, to put as much energy as you can into working them. You could also set aside a special "tricep day" to work them an extra day in the week. Just be sure that you leave a day off between tricep work. You could do some heavy tricep bench presses (keep elbows in), followed by some lying extentions, followed by light kickbacks to failure.
If you have weight workouts on DVD, chapter around so that you do triceps before biceps instead of leaving them to the end, like some workouts do.
Kickboxing or boxing is a good cardio workout that helps tone the arms at the same time. Focus on jabs and crosses, which will engage these muscles either to initiate the movement, or to "put on the brakes".
Tricep dips may work, but I usually don't do them because of wrist and shoulder issues (wanting to prevent recurrences of carpal tunnel and shoulder tendinitis).
S&H Triceps and Biceps, PS Chest, shoulders, triceps and PUB!