Today I am modifying my workouts with some advice from a couple of sources. I recently got hold of a book from human kinetics called target bodybuilding.
This book shows MRI scans of muscles immediately after certain exercises so you can see exactly what exercises stimulate what muscle groups. Some times the results are quite different from what you would expect.
For example to specialize on my upper arms I should do curls with an arm blaster, and weighted dips for triceps. Those two exercises hammer all of the upper arm muscles.
The other change I am making is to increase the work done per workout. Essentially this means using exercises that expend more energy to perform according to the laws of physics.
An example is doing squat instead of leg press, or deadlift instead of leg curl for hamstrings. Clean and jerk, bench press with free weights. Multi joint exercises with free weights that have a greater range of motion are recommended.
The result is a more intense workout that uses more energy. More info can be found in the “truth about abs” ebook advertised on this site. Basically the ebook recommends high intensity training rather than cardio and shaping style workouts.