- Give your arms their own day of training and alternate the exercises between bicep and tricep to keep blood in the general area (ex. barbell curls > skull crushers > preacher curls > pushdowns > etc etc.)
- It might help to do 3 to 4 sets of tricep and bicep work on complementary muscle days (ex. pushdowns at the end of your chest or shoulder day, and concentration curls after back day). These sets should be about concentration and getting a pump, thus high volume.
- As a tip, try to do a couple of tricep exercises where the triceps are stretched (e.g. overhead extensions, lying pullover presses, etc). Triceps take up 2/3 of your upper arm's muscle mass, and if you're a hard gainer doing this will be an effective stimulus.
- Try starting your arm workouts with isolation exercises, and then do bigger compound movements. Its possible that you might need to improve your mind-muscle connection.