It's sometimes confusing when to use direct heat versus indirect heat
when grilling, and how to achieve that with a gas grill. Well,
thankfully, it's easier on a gas grill than on a charcoal grill.
You should always preheat your grill with all burners on their highest
setting for at least 10 minutes before starting. Then, turn off one
side of the grill, and put the food on that side. It couldn't be
easier to cook indirectly.
Some experts recommend turning the food often when you're cooking
indirectly on a gas grill. They say it's because the food is not going
to get the same heat from all sides like with a charcoal grill where
you make a ring of coals around the outside and cook in the center.
Other experts feel you should leave the lid closed for as long as
possible and let the heat do its job.
I have found through my experience that having the heat on only one
side works just as well as a ring of heat, and that leaving the meat
alone will provide a more flavorful and juicy result.
If you're cooking food directly, you will want to turn down the
burners to a medium level so as not to cook too quickly. It's no fun
to bite into a burger that's a hockey puck on the outside and raw in
the middle.
Some good foods to cook indirectly are ribs, turkeys, and roasts. Yes,
they are marvelous from the barbeque and don't heat up your kitchen!
Direct cooking is usually used for items that cook in less than 20
minutes like chicken parts and burgers. Vegetables can be cooked this
way.
In addition, sometimes you want to add in slow burning wood chips to
infuse a nice smoky flavor. Some models of gas grills such as the Twin
Eagle line have an optional smoke box where you put the soaked wood
chips. You can buy small bags of wood chips or a variety and play with
them until you find a mix that you like.
It's important to remember to soak woods like mesquite, alder, hickory
and pecan for at least one hour before smoking. This prevents the wood
from burning too quickly and creates a nice aromatic smoke.

http://groups.google.com/group/arcook/