There have been many theories over the years as to how to build serious pipes. Guys like Arnold and Sergio bombed there guns for hours on end and built some of the sickest arms of all time. Later, the advocates of high intensity training like Mentzer and Yates would do a few of the most insane sets of curls using weights mere mortals don't use on the bench press and call it a day for biceps in a matter of minutes. These two theories have a single underlying theme in common: To build the guns of a champion, you've got to train your arms hard and heavy.
You want arms, you gotta avoid the laundry list of exercises with a predetermined set and rep ranges. Sure, you know you need the free weight basics: barbell curls, dumbbells curls, preachers, hammers, skull crushers and the like. Experiment with rep ranges. Try some high rep sets of 15-25; do some sets so heavy that you'll need a spot on your third rep… it all works. It just doesn't all work all the time. Instead of all the usual recycled bullshit, examine some intensity techniques and exercise tricks you can do to hit those deep fibers and to give you that last inch or two you need to achieve true freakdom.
Exercise 1: Running the Rack
Exercise 2: Dropset 21s
Exercise 3: Buddy Curls
You hear the weak excuses all the time: “No matter what I do, my arms won't grow” or “It's not my fault, I have shitty genetics” or “I think my arms are overtrained… from now on I'll do six sets for arms every other month.” These are all copouts. The bottom line is that you don't believe you can build great arms and thus you never will. It applies to every facet of life. Genetics or luck or privilege mean nothing in the face of a positive attitude and a relentless will. If you are truly hungry to succeed and are willing to accept nothing less of yourself, then all out, balls to the wall effort, then you cannot be stopped. Those arms you see as you close your eyes each night are out there waiting for you. Now it is simply a matter of whether or not you've got the balls to go get them.