This could either be a muscle you feel is generally weaker or a body part that you simply wish was larger. Whatever the case, by getting yourself onto a specialization routine, you can bring up this lagging part while maintaining your current strength level for the rest of your body.

Then, after you are satisfied with that one particular muscle, you can proceed to choose another. This also adds variety to your workout routine and helps keep the motivational levels high to get you continual results.

Here are the basics on setting up your very own specialization routine.
frequencyThe first thing you must consider with a specialization routine is the frequency of your sessions. While you are definitely going to be focusing more intensely on one or two particular body parts, you must still ensure that you are giving them enough rest in between sessions so that they can grow back stronger.

A good approach to take is to pick two key body parts that you really want to target; one being an upper body muscle and the other being a lower body muscle.

All the other parts of your body will be put on a low-volume maintenance protocol so that you can devote more energy toward training those chosen muscles, as well as recovering from your workouts.

You'll likely find the best results if you train the body parts you're specializing two to three times in a seven-day period. If you choose to train them three times, you will go on a full-body workout program; and if you choose two times, you'll do an upper/lower split set-up. The two-times-per-week setup generally works slightly better with specialization routines because it allows for a little more volume with each workout session.
workout designAfter you've chosen the focus muscles, you will include one compound lift for that muscle, lifting in the rep range of 5-6 for 4-5 sets, total.

Next, add in two to three isolated exercises for that same body part, performing 2-3 sets of 8-12 reps.

Basically, what you are doing here is first performing a heavy-tension exercise, followed by a few exercises that will apply a good fatigue stimulus. This combination is what's going to get the muscle to grow stronger, and larger as well.

The rest of your workout, since it's on maintenance, should consist of mostly compound movements, performing 2-3 sets of 6-8 reps.

Check out a sample specialization routine and find out how long to maintain it.

Chest/quad specialization upper/lower routine
So, for example, let's say you choose to do a chest and quad specialization routine.

This is what your setup would look like:

Monday: Upper
Tuesday: Lower
Thursday: Upper
Friday: Lower

Monday/Thursday workout:
Chest press: 5 sets of 5 reps
Incline chest press: 3 sets of 8 reps
Pec flyes: 2 sets of 12 reps

Bent-over row: 3 sets of 6 reps
Shoulder press: 3 sets of 6 reps
Bicep curls: 2 sets of 8 reps

Tuesday/Friday workout:
Squats: 5 sets of 5 reps
Leg extension: 3 sets of 8 reps
One-legged squat: 3 sets of 8 reps

Hamstring curl: 3 sets of 6 reps
Calf raise: 2 sets of 12 reps

Notice in the above workout scenario that your core lift is done first so that you are freshest for this movement, since this is where you really want to try and max out your weight. 

On a week-to-week basis, you should be focused on loading as much weight as you can onto the specialization exercises, while keeping the other exercises in the program constant (some weight can be added; however, this is not the main objective). 

The more weight you add to the other exercises, the less energy reserves you'll have available to recover from the specialization lifts, thus potentially decreasing the rate of improvement you experience.
durationThe total duration of your specialization routine should last for 4-8 weeks, at which point you should drop back on the total volume you're doing for the chosen parts, while keeping the intensity up (total weight lifted). Proceed to do this for another two weeks (other parts are still at maintenance), and then if you'd like you can switch over to a new program that is going to specialize in two new muscle groups.

Note that, in some cases, your core compound lift to start with will be the same since it will work multiple body parts at the same time.

For example, if you're doing a tricep specialization, you may begin with a chest press again, but then proceed to do tricep extensions followed by an overhead tricep press as the other two isolated lifts.

Finally, keep in mind that, as with any workout protocol, after three months of lifting straight you should be taking one full week off of all lifting to really let your body fully recover. You can still be active during this week -- and should be -- just don't try to progressively overload any body parts since the whole point of this break is to allow for any supercompensation to take place, and also to prevent overtraining from setting in.
make workouts specialIf you feel as though your workout needs a change or you just can't seem to improve a certain body part, give a specialization routine a try to reap the rewards of concentrating your workout and your body on specific muscles. 

Billy P., New York, NY