When training my arms I always try and focus on the mind to muscle connection.
I went through a stage in my training where I wasn't happy with the size and shape of my arms so I would always try and increase my intensity by upping my weights trying to curl the heaviest weight I could possibly lift, thinking that this would be the the answer.
This just left me with many years of frustration and injuries.
Focus on stretch and contraction
What I've started to do now is drop the weights and really focus on the stretch and contraction of whatever movement I'm doing and this has made all the difference for me in my arm training.
|2/3rds of your upper arm consist of triceps|
I've also started doing less bicep exercises and more tricep exercises, so where I'd normally do one set biceps and one set triceps now I'll do one set biceps and two sets of triceps. Looking at it now it does make sense to train upper arms like this seeing that 2/3 of your upper arm consists of your triceps.