Being on the ground, you serve as a look-out for the climber, among other things. You may see some hazard that he does not (and vice-versa). You serve as the primary safety when dealing with car and pedestrian traffic.
When you get really good, you'll pretty much be able to work without need for much communication... you'll be able to tell what the climber is going to need before he asks for it, whether it's a refuel, a lowering rope, or whatnot.
It is up to YOU to elevate yourself from being a "lowly groundie" to making yourself an invaluable part of the team. Groundies like that can get pretty good pay for never leaving the ground. Mine certainly do.
I ask alot from my groundmen, but those who do the job well are well-respected. It takes alot to keep up with me, and anyone who can has *got* to be busting rear. Not to mention putting up with me, but that's another story...
Ditto to Ax on letting ropes run when possible. If you ever really want to know why we find this important, crawl inside a dryer and set yourself to tumble for a few minutes... yes, it feels THAT bad.
Customer skills can be important, along with appearance. 90% of the time, YOU'LL be the one that gets approached with a problem or by the neighbor looking for an estimate. You're the one on the ground, and the most accesable.
Good groundmen don't let the chipper run for long periods while not chipping. You'll find that to be another pet-peave of most climbers and owners.
If you don't have one, read a comprehensive employee safety manual. The life you save will likely be your own. E-mail me for mine in case you or anyone else would like/need to read it.
Oh, and have fun... life is too short.