Every trainee is on a different level, over the years different training systems are employed. In the initial period of the strength activity you can observe a tendency to over-burden chest and shoulders' muscles. Indeed, for many young men it is almost a personal tragedy if they observe lower performance on the bench. It is a very rare occurence that people who have just started their workout involve evenly upper and lover body. Fortunately, the idea of training of selected body parts only is slowly being replaced with modern full body workout plans and split trainings.
You should definitely read:A mile-wide back now! - Part 2
An 8-week plan:
Twice a week do 5 sets of inverted rows on each session. In each session do the maximum number of repetitions. If you reach the level of 15 reps without any additional weight, add 5 kgs on your chest. If you can do 10 reps with 5 kilos, add 10 kilos. Minimal threshold for upgrading to a higher lever is 10 full movements with 20 kilos on your chest. Don't jerk, don't cheat, let your upper body work. The weight should be lifted by your strength only.
Additionally, aside from inverted rows, on each session do 3 sets of pull ups. If you are too weak for a whole movement up, do only the negative phase (using a bench, your mate's help or by jumping up to the stick level). In this case, if you do only the negative phase, the tempo should be 4 seconds. Do at least 5 reps. In the following weeks try to add as many reps as you can in successive sets.
A wide grip or narrow? What is better for wider back?
The most commonly repeated myth the Internet is full of is the necessity to use a wide grip in pull ups in order to employ the latissimus dorsi muscle. Unfortunately, there is a very poor support of this theory in scientific research. What's more, a well-renowned portal: exrx, in their recommendations analysing kinesiology, points to the too wide grip as a major fallacy in multi-joint exercises (such as: bench press, incline press, lat pulldown, pull ups, upright row)! 
It has been discussed for example by a legendary bodybuilder: Dorian Yates (one of the greatest competitors ever) a six-time Mr. Olympia (1992,1993, 1994, 1995, 1996, 1997):
He mentioned that a wide grip limits trajectory of your movement, and engages upper part of your back, teres minor and major muscles more than the latissimus dorsi muscle. He said that during his workout he would employ a standard or narrow grip focusing on keeping elbows possibly straight down or a bit back, depending whether it was a vertical or horizontal movement. A vast majority of training men engages mostly the rhomboid and the trapezium muscles, hence you can see many competitors with well-developed upper back and relatively few with their backs envenly and entirely built, Yeates mentioned. 
You are the weakest with a wide grip, and the engagement of the latissimus dorsi musce is comparable with a narrow or standard grip. Some research has shown slightly higher activation of the latissimus dorsi muscle with the wide grip but only in the eccentric movement phase. An overall analysis indicates that the grip width is of no importance for the development of the latissimus dorsi muscle, while applied weight in case of the wider grip will be smaller as a result of inefficient lever. Most athletes raise definately bigger weight when applying a narrow or standard grip (a bit wider than their shoulders).
What is of key importance for the width of your back is not the width of your grip but trajectory of your body. When you pull up, it is essential that you keep your elbows close to your body. If the movement imitates rowing (your upper body evidently moves back), you minimise the effectiveness of the target muscles' work: then the exerciese works more like barbell rowing (emphasis on back's thickness and the trapezius muscle).
Undercling, overhand grip or neutral grip?
You should also consider a hammer grip – it may allow you to lift heavier weights. Undercling is risky due to a bigger chance of an injury to the biceps.
In one study (Norway, 2014)  muscle activation was compared with load of 6 RM (6 reps max.) in the lat pulldown. 15 men would do this exercise using narrow, neutral and wide grips.
The results were as follows:
first observation indicated power loss with the wider grip. The examined would lift the biggest weight with the narrow (80,3 ± 7,2 kg) or medium grips (80 ± 7,1 kg). The wider grip produced the weakest results and the smallest strength: 77,3 ± 6,3 kg. This is actually important during the lat pulldown, but its importance is collosal in case of pull ups,
regardless of the grip width, if both phases were analysed (concentric and eccentric) – activation of the latissimus dorsi, trapezius, infraspinatus muscles was similar,
higher activation of the biceps has been found in case of the standard grip versus the narrow,
finally: in case of the split movement, in the eccentric phase the latissimus dorsi and infraspinatus muscles did the biggest workout with the wider grip when compared to the narrow,
greater work of the latissimus dorsi was noted in case of the standard grip when compared to the narrow grip,
greater engagement of the biceps was noted during standard grip exercising vs. the wider grip.
Pull ups are the most important exercises for a mile-wide and rediculously thick back. The remaining will be described in succeeding articles.
Read part two: A mile-wide back now!