Weakness Is A Crime

Build a big V.

 Everyone loves a V-taper, adding size to your lats makes your waist appear smaller too!
Try adding the “scapular depression” to your next set of pulldowns. To do this, take a slightly wider than shoulder width grip on the Pulldown bar, and set the weight to something you can do 8-10 reps of pulldowns with.

Instead of doing a Pulldown, lock your elbows, and pull your shoulder blades down by squeezing your lats hard. (This is a short range movement, only a few inches, and can be difficult to master, so don’t get discouraged) When the lats are fully contracted, and the shoulder blades are down as far as you can, hold the contraction for a second, and then raise the weight to the starting position. Do 10-12 reps, and then continue with a set of pulldowns using the same technique to start the movement. Do not go to failure. Stop 1 rep before you think you will hit failure. This is very taxing on your lats, but will product great results.

The scapular depression can be used as part of your back training as a stand alone exercise too. If you choose to do this, use as heavy a weight as possible, without swinging your body. The lats are very strong once you learn to use them, and can handle tremendous weight on this exercise.
Add this in, and watch the lats grow.