The triceps, like any other muscle group, should be trained at least twice per week on nonconsecutive days. This three-part muscle at the back of the upper arms extends the elbow and is activated by exercises such as pushups -- especially the diamond variety; close-grip chest presses; overhead or lying extensions; and kickbacks.
You're eager to achieve the horse-shoe shape at the back of your arms -- present when your triceps pop -- but don't want to wait forever for it to form. Patience is the key to muscle development, however. When you lift weights, you stress the muscle fibers, which causes a host of physiological reactions -- including muscle cell breakdown. When you rest, the cells repair and grow stronger giving you the triceps you desire. If you train the triceps too often, they never have a chance to grow stronger. University of New Mexico professor Len Kravitz notes that muscle adaptation begins right after training, but it can take weeks or months for results to show.
If you're doing a split routine, in which you work specific muscle groups on different days, leave at least 48 hours between triceps exercises. Don't forget that on the day you work chest and shoulders, you're also using a lot of triceps, so plan your workouts accordingly. For example, you might train biceps and triceps on Monday, legs on Tuesday, chest and shoulders on Wednesday, triceps again on Thursday and back on Friday. In this example, you could sneak in an additional triceps workout on Saturday. If you do total body routines, aim for every other day.