Shoulders & Triceps
Chest & Biceps
Chest & Shoulders
Triceps & Biceps
That way ^ gives your arms more "hits", indirectly and directly (and more importantly, you can give them more intensity/focus while they're fresher in the workout which is often the problem for lagging parts). The first split would be best though if you want to bring up over-head press, just keep the volume low enough.
If you are advanced enough, what you'd look for is good recovery partitioning - that is, giving more attention/exercises/volume for certain lagging bodyparts while lowering the volume for good parts.
Don't forget actually feeling the arms work good too. Some people swing the weights about, then wonder why their arms are lagging, then they'll go around changing crap that didn't need to be changed lol. Personally, my arms respond better to high[er] reps, something like 10-12 reps, or slightly more for biceps (can focus on them better, and it's easier on the joints etc).