Impressive arms- some have em, some don't. The peculiar thing about it is, just about everyone goes into the gym visualizing a massive chest and arms, and normally end up taking a terrible route to reach their destination. Now, to cover some basics -
1) if you dont have your diet down, you wont grow. I dont care what you're lifting, how many times. if you arent eating, you arent growing.
2) Proportions, Proportions, Proportions. If you want your arms to get humongous, guess what you need to pay extra special attention to (heres a hint, it isnt the biceps). Thats right, it's the triceps. Whether you are looking for size, strength, Growth in inches, to look better from different angles, etc - MOST of the time, you weakness in the arms will be the triceps.
3) At the beginner stage, there is Biceps, and there is Triceps. As you grow, you will develop a need to pay attention to the muscles OF the biceps/triceps. Thats right, it isnt 1 muscle. The triceps in particular is composed of 3 main heads (The lateral head, the Medial, and the Long head) that are affected differently depending on your angle or your movement.
Now FTR, id like to once again say "To each their own." What i do is what i have taken from dozens of bodybuilders and molded into my own style that works fantastically for me and those i train.
Lets begin with the Biceps-
You say they arent growing, you say they dont respond to training. Well, first question id ask is "how often do you measure your arms?" or better yet, "how often do you measure your biceps Singularly?" One's arm wont grow in a workout, a week, a month, etc. If you are not a complete beginner and are past the point of initial growth, putting an inch on your arms will take time, a good amount of time. Time that must be filled with constant fuel and work.
2nd question id ask is "just what are you doing for your biceps?" If you respond with some half assed routine with All of half blown movements and some silly rep/weight ratio, Imma slap you. Now i dont have amazing arms, but they are 20 inches, so i must be doing something right. MOST of the time i am training heavy. A Fantastic bicep movement for this is Barbell curls. The beautiful part about barbell curls is they can evolve into Cheat curls. A cheat curl is essentially a barbell curl with a bit of swaying thrown in. The trick is to MAINTAIN the stress on the bicep through the entirety of the movement. Another movement i normally include is 1 handed Preacher curls. The thing about these is you need to ensure you are actually using the preacher curl bench properly, concentric contraction vs eccentric contraction, allowing your bicep to fully extend before contraction it to the top again.
On to Triceps-
Now, the triceps can be a bit tricky, they are for me atleast. Why you ask? Quite simply put, After my discovery of the need to hit them in different ways to affect the different heads, i thought i was working heads that i actually wasnt. My Triceps Long head is huge, my Lateral head is slowly catching up. For the beginners out there reading this, i suggest you take this opportunity to start applying more focus to your Tricep lateral heads. A way ive read and applied to doing this is simply doing tricep extensions, but pushing the bar away from your body. When you start to focus on the heads of a muscle, it really becomes about feeling it out. It can change from person to person, so you need to find your niche. If we are speaking in terms of just general great triceps exercises, my top favorite 3 would have to be :
A. Dips- I love dips. I do them weighted, bumping by 25 and 45lb plates. I find the trickiest part of dips for me is that i enjoy them for both chest AND triceps; HOWEVER, i do chest and triceps on separate days. So to solve this, i simply have to bend more or straighten myself, and use specific ROMs for the targetted muscle.
B. 1 Armed Overhead Dumbbell extension- A fantastic movement that allows you to get a full, complete ROM, and isolate your triceps, WHILE simultaneously minimalizing possible cheating. You'll find that aside from cheating yourself with your ROM, it is pretty difficult to cheat in a movement while holding a dumbbell overhead.
C. The Tricep extension, with a Push away from body focus- Now, in an attempt to bring my Lateral head up to speed with the others, this movement is becoming one of my favorites. I used to love tricep extensions early on, but i reached a point where the cables just werent heavy enough, and i soon chose other movements. Then i simply began doing these movements on the Lat pulldown cables, and Viola, its back on the list.
In a Nutshell i say this: Focus on your proportions and symmetry. The earlier you catch this, the easier it will be. And also find what works for you, the answer for some might not be the answer to one. Happy lifting.