From someone who has fairly large arms - there is no secret....just train them - train them hard - be consistent - yes I go through phases where I will do X exercises but alot of the time my sessions will change everytime I step in the gym...also if your focusing on biceps to get big arms then your doing it wrong....focus on triceps.....
compound movements
isolation movements
high reps
low reps
light weight
heavy weight
Just do it all and the results will come....