The dumbbell row is a staple, so don't screw it up.

What NOT To Do:

Here I'm kneeling on a box and chicken-winging the arm. Most people will pull straight up on this move, working more of the posterior shoulder muscles and upper back, completely missing the meat of the lats.

What To Do:

Do this free standing so your core is more activity involved and you're working the legs for a bonus. The key point here is starting the dumbbell near or past the toes to get a full stretch of the lats and dragging the elbow back and up in an arching "J" shape. Lead with the elbow to get a nice, full contraction of the lats.

There's also a rotation component happening here since we start further forward with a slight shoulder rotation toward the midline and end with square shoulders, working the obliques and core.

Related:
4 More Back Exercises You're Screwing Up

Related:
5 Lat Exercises Everyone is Doing Wrong