Only bodybuilders should do an arm day. My arm day is my rest day, when i get so bored from not lifting i go out to the garage and do a bunch of curls. Arm isolation exercises are largely a waste time and effort. I arms get plenty of work from bench pressing, pushups, chin ups and dips.
Everything you need for your arms you should be getting from chest workouts and back workouts. Everything you need for triceps, you should be getting from pushups and dips.
I might curl once a week, if that and my arms are shredded and vascular. Here a very quick overview of what are effective splits.
Beginner Split:
Legs
Rest
Chest
Rest/Cardio
Back
Rest
Intermediate Split
Legs
Chest
Back
Shoulders
Core & Arms
Rest
In terms of doing an upper body routine:
If you're in the beginner category, you should do mostly chest exercises and one shoulder exercise. Example: flat bench press, incline bench press, dips, pushups (varying hand positions), and for shoulders so a standing military press. Work your chest first and your shoulders last since your chest is much stronger than your shoulders.
If your'e in the intermediate category, you should do a separate day for shoulders because you likely have developed front delts and triceps and your rear delts are being neglected. Also because you're lifting heavier weights, your rotator-cuff will be taking too much stress for you to do chest and shoulders on the same day.
My shoulder day is comprised of maybe eight different shoulder exercises. Once you have developed shoulders, you'll want to target specific delts to keep them balanced. The front delt tends to develop much faster than the others. You'l need to spend most your time strengthening the rear and middle delt, cause the front will get plenty of work from all your chest workouts.
Example: Standing Military Press, Arnold press, Standing Lateral Raises, DB vertical rows, Rear Delt Fly
You're going to get more from these exersices if you doing standing variations rather than sitting. Always choose to stand rather than sit. This builds core strength, stabilizers, balance, symmetry and gives you the best view of any ladies
Proof I have arms