How can I stretch my lats?

A great way to stretch the lats is to perform the ball lat stretch.  Use the technique described below to perform the stretch. Kneel in front of a stability ball with one arm on the ball (thumb pointed up), and other hand on the ground.   Next, try  to round the lower back by tucking the butt toward the heels and reach forward with the arm on the ball until a stretch is felt along the side of the torso and into the lower back. Hold for at least 30 seconds and perform on opposite side. If a stability ball is unavailable, this stretch can also be performed standing while holding onto something stable.  

A good stretch for the lats is to use a physio ball and place your hand on top of it.  Keeping your arm straight and your body in a table top position (on knees), allow yourself to drop your weight into the shoulder of the arm that is on the ball.  If you don't have a physio ball, a chair will work just fine.  You should feel the stretch throughout the entire lat.  Hold this stretch for 10-30 seconds and repeat on the opposite side.