Proper glove fit and grip selection are important for reducing arm pump.They will also reduce blistering, cramping, and numbness as well.
A glove that is too large will allow your hand to move around inside while the glove stays in one place on the grip. This will lead to gorilla grip and blisters. A glove that is too small will restrict your movement and blood flow, leading to cramping and numbness. Keeping your gloves clean and dry is important for obvious reasons.
Grip selection is important too. My '04 came stock with Renthal half waffle grips. Nice grips, but the smooth top just didn't hook up well with my gloves. My hands would move around on the grips and I tended to squeeze the bars too hard trying to keep them in one place. It just got worse the faster I went. I switched to a set of Oury grips with raised ridges about 3/16" tall all the way around the grip and noticed a night/day improvement. They look like they'd be about as easy on the hands as a meathook but they really do stick to my gloves well. Now I don't have to squeeze so hard to to feel in control. I get a solid, more consistant grip, which lets me relax and keep my elbows up. I've noticed a dramatic reduction in fatigue and wear and tear on my hands. Lap times, too. (I'm still slow) All from a simple grip change.
My 2 cents.