Whenever you lift weights you reach certain plateaus so you have to make sure you vary your excercises.

One of my favorite and most effective is manual resistance. This very effective but you have to put aside the fact that you will look silly. You need a partner for this and a bar. You basically do all the essential lifts that you normally do but you do not use any weights.

Straight bar curls- Curl while your partner puts a small amount of pressure on the bar as you pull up. Do not stop there, but reverse your motion downward as your partner now resists on the bar upward as you extend downward. Repeat until your partner is able to let go of the bar. Your arms will be burning and the whole gym will be watching you struggle to lift that little bar.

 21's are phenomenal! You curl from your waist a third of the way up 7 times, from there you curl from half way up all the way to the top. Finally you complete your curl from top to bottom.

Make sure you do routine curls like the Preacher curl( Preacher curl works great with manual resistance makes you feel like a weakling) and the Hammer curl.

The Incline curl is exceptional- Lie down on an inclined bench and do curls at an inclination. You will have to do less weight on these. Don't try and be a hero on any of these proper form is better than more weight! 

Do's

Stretch

Change up routine

Eat right protein and Carbs

Rest your body

Don'ts

Don't blow your whole workout by eating a candy bar afterwards

Don't over do it

 Glutamine is a great supplement, It helps your muscles recuperate quicker. The only side effects my friends and I noticed where what we called the glutamine bombs. A powerful gas release that will quickly clear a grocery aisle. Whats a little gas when you have nice looking arms.