The back is a huge powerfull muscle group that is the single biggest factor in determining how large you appear. Nasser El Sonbaty might've been Mr Olympia this last year if it wasn't for an underdevelopped back. Make sure you devote equal attention to those muscles as you do to your chest and abs.
The man who practically defines the word huge is Dorian Yates. His back is probably the best that bodybuilding has ever seen. Ever. His secret, if it can be called that, is to train the back by itself. I personally consider my back day to be the most taxing of all my workouts. Take a look at my back routine and you'll see why.
On to the exercises...
Perhaps the most important and most difficult mass builder there is. For this one, you need to have a belt. I also recommed getting someone to show you how to do them rather than reading this and trying it on your own. No joke, it's a dangerous movement if performed wrong.
Load up a barbell either on the floor or on the outside edge of a pair of squat rack handles so that you can pick up the weight and step back. Grab the weight with an overhand (palms towards you) grip. Keep your arms straight throughout the movement. Look up. Keep your back flat. Bend your knees and lower the weight until it rests on the ground. Straighten your legs and bring your back up to a vertical position at the same time. Don't bend your arms at this stage or any other. Put the weight back down and do it again in the same manner
Try to lift the weight up as high as possible without leaning backwards at the top of the movement. I go so far as to shrug the weight up half of an inch farther before I lower it down again.
Lower back, quads, hamstrings, buttocks, trapezius... almost everything.
This exercise is extremely hard. You should be about ready to die after you finish your last set. Because it's so hard and you're lifting so much weight, make a special point of warming up with a set of 15 to 20 hyperextensions and stretching your lower back and legs after that.
The deadlift and squats are the two most important mass building movements you will do. Make sure you give them your all. Also make sure you do them properly.
Crouch down so that your back forms a 45 to 60 degree angle with the floor. Bend your knees and flatten your back, tilting your chin up will help you avoid arching your back. With an over or underhand grip, pick up a moderately heavy barbell and let it hang just below your knees. Pull your elbows back as far as possible using your trapezius and back muscle to lift the weight to your mid-rift. Lower and repeat. Keep your upper body as still as possible doing this movement. You won't see any gains if you bring your chest down to the weight rather than the weight up to your chest.
Upper back, trapezius, seconday stress on forearms/biceps depending on if you use a palms-in or palms-out grip respectively.
This is a fantastic movement for building a wide, powerfull back. I include it in almost every back workout I do.
Execute this movement similar to the bent over row. Stand over the T-bar row machine with your back slightly arched up. Grab the handles and pull the weight up as high as you can before slowly lowering it. I recommend using a belt on this one because it's pretty rough on the lower back.
Unlike the bent over row, I tend to position my upper body much closer to horizontal when I perform this movement. The reason for this is that the machine you use for this exercise guides the weight along an arc that encourages that particular stance over any other.
Lower lats.
If you have a choice between using a T-Bar row with a pad and one without, take the one without the pad. I feel that having a pad against your chest inhibits breathing and turns the exercise into a different movement that doesn't put as much stress on the lats.
This is a great width building movement, but it is extremely difficult. If I include this motion in a workout, then I will leave out bent over rows simply because doing these two plus deadlifts would leave me nothing for the rest of my workout.
Take a seat at the low pulley row machine and pickup the handle with both hands. A narrow grip will serve you better during this movement, so choose a grip accordingly. Keep your legs almost totally straight, but there's no need to lock them. Start with your arms extended in front of you and your legs straight.The weight should be pulling your body so that it is folded over. Straighten your body to the point that it is perpendicular to the floor at the same time as you pull your arms back and bring the handle to your sternum. Roll your shoulders back and stick your chest out over the grip to maximize the contraction. Lower the weight slowly and allow the weight to stretch your lats at the bottom of the movement.
Lower lats
A lot of guys think wide grip lat pull downs is the movement to do if you want to build width. I think the low pulley row is the best way to go. Nobody has every built a great back without gritting their teeth through several sets on this thing every week.
This is an exercise that's very easy to do, but very difficult to do effectively. You may have been doing lat pulls for years and been cheating yourself out of muscle growth by not heeding some simple, but seldom heard, guidelines.
First, as with all pulling movements, your back should be slightly arched throught the entire movement. Lean back slightly on the seat once you've secured your legs. The reason for doing these things is so that you minimize the role of the biceps in the pulling motion. People who round the backs at the bottom of this movement tend to believe that they are accomplishing something by pulling the weight down another inch. Unfortunately, it is their abs and biceps that power the weight through that final inch and the fact of the matter is that they need to drop the weight to something their lats can pull on their own if they want to see any gains.
Now that you're situated. Take a shoulder width or narrow grip on your favorite handle. A popular missconception is that using a super wide grip equates to growing a super wide back. This is not the case. Growth is going to stimulated by total muscle contraction which can only be achieved by using a grip that lets you pull your elbows as far down and back as possible.
If you feel your biceps are picking up too much of the stress during this movement, try putting your thumbs over the bar on the same side as your fingers. This "deactivates" the bicep and makes it harder to bring that muscle into play. If your grip is failing you, then you'll have to use straps to get the most out of this.
Once you understand all of this, the actual performance is almost trivial. Pull the weight as far down as you can. Squeeze your elbows back and pause for a moment before lowering the weight.
I think the negative portion of the rep is the most important part of this exercise and I'm always sure to spend two to three times as much time bringing my arms up as I do pulling them down.
Upper lats.
A great lat movement, but not the only lat movement. There are a lot of grip options to play around with for this exercise. I like the triangular pieces myself, but make your own decision based on which grip permits the most range of motion and minimizes the role of by the biceps.