I (Dave) really have no idea how to use the grill - so this doc will likely change over time. The following steps are drawn from the user manual.
Assuming the grill is off and cool, remove the slide out grease catch pan and check the disposable aluminum drip tray for too much grease. Replace when necessary. (How much is too much?) (Where are the replacements stored?) Reinstall the slide out grease catch pan and drip tray. Need pic.
Open the grill lid and look at the two cooking grates. The two sides of each grate have different surfaces - one side is "pointed" and the other side is "flat". See below pic. Flip the grates as needed to get the surface you want to cook with. (The grate cross section is a triangle; one side gives you the pointy top of the triangle, and the other side gives you the flat bottom of the triangle. I read on the web that food sticks less to the pointy side.)
With the grill lid open, check that both burner control knobs are in the off (O) position. Push each in and turn clockwise so the red indicator is pointing at O. See below pic.
Turn the gas line on at the house. See the below pic. The black hose is the gas coming from the house. The gray hose is the gas going to the grill. When the top of the black swivel-knob is crossways to the gray line (as it is in this pic), the gas to the grill is off. When the top of the black swivel-knob is parallel to the gray line, the gas to the grill is on. Rotate the swivel-knob so that its top is parallel to the gray line.
Wait one minute. (I have no idea why.)
Light the left hand burner. (Do not lean over the grill when lighting!!!) In the below pic of the left hand control knob, the little lightning bolt pushbutton is the igniter button. Push in the left hand control knob and turn it counter clockwise 90 degrees (see below pic). Push and hold in the igniter button - you will hear it clicking. Sometime in the next 15-20 seconds you should hear a whoosh as the left hand burner ignites. When this happens, release the igniter button (stop pushing it).
Light the right hand burner. Push in the right hand control knob and turn it counter clockwise 90 degrees - so it looks just like the left hand knob. You should fairly quickly hear a whoosh as the right hand burner ignites. (The right hand burner ignites using the already-on left hand burner - so you don't need to push in the ignition pushbutton.)
Close the lid to let the grill preheat. The manual says to preheat the grill for 10-15 mins or until the temp reaches 500 degrees. (Note from Scott: I don't wait 10-15 minutes to cook. I let it get hot, then brush grill and start cooking.)
Cook food. Once the grill preheats, cook your food. Adjust the control knobs down from high as appropriate. (Like a gas stove, the further you turn the control knob the lower the heat.) If you only need one burner, you can turn the right hand burner off and just use the left hand burner.
Remove food.
Clean grill for the next user. Turn burners on high for 10 minutes. Brush grill with wire brush. Turn burners off - push in and turn both knobs to the off position.
Turn the gas line off at the house. Rotate the black swivel-knob so that its top is crosswise to the gray line.
After grill cools, cover grill.