The September, 1951 issue of "Your Physique" magazine contains a great article on forearm building from two-time Mr. America winner Alan Stephan (NB: He won both in the AAU and IFBB.)
Stephan was an impressive physical specimen but as was the typical order of the day, his muscles weren't just for show, he could actually do things with them. Case in point is the fact that he could curl 190 pounds in strict form at a bodyweight of 200 lbs.
As the article mentions, the fact that grip training always pays dividends in full body strength was taught to him by the great Steve Reeves. It is no stretch to think that a strong grip and forearms was a big part of Stephan's curling ability so any work in that area will certainly pay dividends. In case you don't have your copy of that issue handy, here's the exercise selection and a few tips from the man himself.
EXERCISE 1: THE REVERSE CURL:
"This movement is for the front and sides of the forearms as well as the upper arm, the brachioradialis muscle. It MUST be performed slowly and deliberately with every bit of mental concentration on the muscles worked. Start off with a weight you can handle easily for 3 sets of 8 reps and work up to 3 sets of 15 reps."
EXERCISE 2: THE WRIST CURL:
"Perform this movement slowly and contract the muscles fully with each movement. Start with a weight you can handle for 3 sets of 10 reps, working up to 3 sets of 20 reps before increasing the weight."
EXERCISE 3: PLATE CATCHING:
"Hold the weight with the palm of the hard towards you then let go and catch it with the other hand. Continue with this exercise until you fel it is no longer possible for you to keep a grip on the weight. Three sets of this exercise should give you plenty of gripping power."
EXERCISE 4: WRIST ROLLING:
"The main objective is to build up all the wrist turning and gripping muscles of the hands and forearms. Roll the weight all the way up and then LOWER SLOWLY
and repeat. Perform three sets with hands turned palms up and three sets with hands palms turned down."
Two important things stand out here: One, that these exercises can be done in pretty much any gym in the land and two, the focus on concentration and getting the most out of each set. Bottom line: there's no reason why anyone couldn't improve his or her forearm strength considerably with this advice and a willingness to put in the work.
Now that you are in possession of this information,what happens next is up to you...