Pretty much everything you do upper body wise is going to help. The wrists and forearms only contain small muscles, so growth and strength gains might take longer than a larger muscle like the shoulders or chest. Still, push ups (maybe go to knuckles or fingertips to involve the wrist more) pull ups or reverse pull ups, deadlifts, etc... are all going to work those muscles.
Back in the day when I was lifting all the time I would do some specific isolation exercises for the wrist and forearm. I've come to the conclusion now that those are pretty useless if you're doing other exercises.