Whatever you are doing in your daily life, you are using your back muscles. So it's important that you exercise/train your back muscles and keep them strong. Your back is the biggest muscle on your upper body, so if you are someone looking to add muscle mass then you should not overlook back training as you will add a ton of muscle as well as increasing your overall strength by working your back.

How often you train your back should be a decision you have made over time, depending on how long your body takes to recover, how good your nutrition is, and what results you are working towards. If you're lifting heavy weights, then you should take two or perhaps three days of resting that body part until you work it again. So training your back once or maybe twice per week should suffice. As for reps and sets, if you're goal is strength, doing three sets of 6 to 8 reps for four of five exercises is enough.

Rows are a must when you want to add strength and size. And most back exercises involve some type of rowing motion such as the seated row, T-bar row, barbell row and dumbbell row. Other exercises include lat pull downs for adding width to your back muscles and back extensions (work the lower muscle group and reverse flies. To get a good all around back workout, choose a mixture of these exercises to hit your back from all angles! You may find, if you are a more advance weight trainer or body builder, that you only need a few good exercises to reach your goal back workout but for a newbie start with rowing, a couple of rowing exercises per workout and then move on to lat pull downs and other less exhausting exercises.

Here are some back exercises and how to do them properly.
Barbell rows. Bend forward to a near squatting position, about 45 degrees. Bring the barbell up towards your mid section, concentrating on squeezing your lats backwards as your do. Once the barbell has touched (or near to touched) your stomach, lower it back down slowly taking full advantage of the negative part of the movement.

Back extensions. Back extensions are a must for strengthening the lower back. Lie on the floor (if you are not in the gym, or course - and they have a back extension machine) with your hands behind your head and lift your chest off the ground.

One arm dumbbell rows. Dumbbell rows are a great way to target the lat muscles and doing them one arm at a time, as in the one arm row, allows you to lift heavier weights. One thing which is key when performing this type of row is keeping your back in proper form and supporting it. So place one foot in front of the other, reverse for which side of your back you are training and then start your row.