Wide lats are all about building up the upper portion of the lats, so it is important to perform exercises, using light weight, that targets the upper portion of the lat through it's movement.
The two movements I prefer to do are dumbbell pullovers and close grip cable rows.
These are the two exercises I've enjoyed ever since I started doing them.
With dumbbell pullovers, you lay on a bench face up, holding a single dumbbell above you with both arms. To initiate the movement, take a deep breath in and let your arms slowly descend behind your head. The objective of this exercise is to give the lats a big stretch under the weight you are holding, and then a nice contract on the way up.
As you let your arms descend behind you, instead of thinking to let the dumbbell go down toward the floor, think of the dumbbell going further away from your head. This takes stress away from your shoulders and increases the eccentric stress on the lats.
The other benefit of performing dumbbell pullovers is that you get a sick pump in the upper portion of the lats, which is where the width comes into play.
My suggestion is to perform 4 sets of 12-15 reps of dumbbell pullovers. Go slow and really focus on feeling the muscle stretch on the eccentric, and contract on the concentric.
With cable rows, you great a great concentric contraction, but not so much a stretch, however, the concentric contraction easily makes up for a lack of eccentric stretch.
If you are lucky, you will have access to a cable row machine which has foot pedals to give you stability, which you will need.
To do a close grip cable row, all you need to do is hold the v-bar handles, or individual handles just closer together, and pull your shoulder blades in, as well as pull with the elbows, to engage as much of the lat muscles as possible.
Bruce Lee was a huge proponent of pullovers to build the lats, because he believed the lats had a huge carryover to punching power. Considering his powering for such a small frame, I won't disagree.