rogue49

wrist curls:
take a dumbell or barbell in hand (i prefer barbell, but everyone is different)
keep it fairly light on weight. (adjust accordingly, you'll get a feel for it)
lay your forearms across a bench, or stand. flat with your palm facing up
you need support otherwise you'll cheat and won't focus.
slowly curl your wrists up & down, and repeat.

reverse wrist curls:
do the same but with your hand facing down
this is a bit more difficult.

this will help develop strength and size in your wrists and forearms.

I like doing them before working on my biceps,
this helps me to focus on that muscle rather than curling with my wrist.
The leverage is better.