I can tell you how not to grill them?

Was visiting some friends of my parents in France (a country known for it's excellent cooking), and they were having a barbecue in the garden.
Unfortunately, they'd misunderstood us, and thought we would arrive an hour earlier than we did.

The father had had an argument with one of his children, and was quite angry when he started to grill the chickens. And here comes the description on how not to do it:

He placed the chickens on the grill, used lighterfluid to get the flames high (the grill had been ready for an hour), then continued to dose the chicknes too. Put a match to it, and left it like that for 10-15 minutes.

Then he serverd the charred carcass' to his guest, and said to his children: "If anyone of you says anything negative about this, it's straight to bed without food!" and it was around 1 pm.
(Let's just say I'm glad I was speaking norwegian, and thus could get away with a couple of comments)

But to be a bit more helpful..

You'll most likely have to turn it often to make sure it won't get burnt. Maybe just put a spit through it, and roll that slowly around. (This is what they do in shops in Norway)
I'd most likey season the chicken first, as it doesn't have much taste alone, but that's up to you.

Sorry, but apart from knowing it took 10-15 min to char the chickens, I have no idea about how long to grill them.

SNGX - If you are using a gas grill, sear the outside of the chicken with high heat and then turn the flame down and cook over low heat for about 10 minutes. The searing helps keep the juices in. Works with meat too.

the key to chicken breasts is to do the steaks first, so the coals are not as hot when you put on the chicken. also, make sure you marinate them good, it helps some what to keep the juices in. for a whole chicken, make a stand using an empty beer can shoved up the cavity, again using non-hot coals and cover it for 45min-1hour until juices run clear.

Empty Beer can? naa, use a full beer, just pop the top and shove it in the cavity. It helps keep the chicken tender and juicy.