Hate me if you must once you try these, but they work.
Pull yourself up on a chin up bar until your nose is level with the bar. Palms are facing you, although you can try the same exercise with the palms facing away from you.
Now hang on as long as you can. Fight it as your arms start fatiguing and you start dropping down. Try for 30 seconds.
Your biceps will scream at you and they will grow,