Just to confuse you, i'll disagree with Oak on the issue of going as wide as you can. The wider you go, the more you decrease your range of motion when working your back.
I suggest you use a medium grip....., generally around shoulder width or just inside shoulder width.
Barbell rows are a great exercise. Try them with your palms up rather than down.....this will let you bring your elbows back further and higher and extend your range of motion which is what is required to fully work your lats.
One arm dumbell rows concentrating on pulling the weight in an arc from your chest to just inside your hip with controlled form.
Close grip pull-ups. I like to get a v-bar and throw it over the top of a chinning bar and do close grip pull-ups like that to transfer the stress predominately to the lats.
You will find that if you do any or all of your back exercises using a palms up grip, you will stress your lats more than you will with an overhand grip, right along the line of the lats
close grip or medium grip chin ups with palms facing inwards make the lats longer.
Wide grip chins make the lats wider.
Make sure when you do the chip ups you get a really hard stretch at the bottom and pull yourself as far up as possible; even getting so high that your lower sternum touches the bar.
Let me clairify myself, I meant to say, go as wide as you can where you still feel the muscle being worked and there is no pain.
When I do Barbell rows, I put my ring finger on the line. thats kinda wide for me. And I feel it all throughout my lats.
But when I do Behind the neck pulldowns, my hands are to the end of the bar, and i bring the bar as far down as i can, usually, to the end of my hair line. Feels good....
close, parallel grip pulldown, keep torso straight, don't lean back, just slightly arc a bit
standing one arm cable rows, with a pulley that is adjustable in height, have the pulley somewhere at a height between hips and knees, turn your wrist as you pull the cable and hold the contraction for a second, i get a better concentrated lower lat contraction than with one arm dumbell rows.
It took years for me to even get them sore let alone grow. Now they look great but I cant figure out why or what it took, I didnt really didnt change anything. They just grew last for no reason.