First off, start by doing some behind the back curls, use heavy weight MAKE SURE U WARM UP then do some reverse curls with a lighter weight, aim for 20 reps, then do some normal wrist curls, aim for 20 also. Do 4 sets of each with 30 seconds rest in between. Your arms will be fried and pumped in no time. Heavy deadlifts are also key in forarm development, DONT USE STRAPS. You can also do plate pinches ( put 2 weight plates together and pinch as long as you can) and farmers walks ( grab some heavy dumbells, maybe 100 in each hand to start out with and try and walk as far as you can) You will be on your way to huge forearms in no time.