Hold a dumbbell in each hand with a supinated grip. Either sit into a partial squat and rest the forearms on the thighs, or kneel and support the forearms on a bench, keeping the hands slightly below the elbows.
 
Allow your wrists to extend, then curl the dumbbells back up as far as possible. You can allow the fingers to extend in the bottom as well to include more direct finger flexor work.
 
Purpose
The dumbbell wrist curl strengthens the wrist and improves grip strength by helping support a better hand position when holding a bar. Using dumbbells increases the demand on wrist control and stability, and helps develop and maintain symmetry side to side.
 
Programming
Generally sets of 10-30 are appropriate.