If you misuse your barbecue, you're literally playing with fire.
First off, take a look at the location of your grill -- ideally; it should be on the patio without anything immediately around it. Don't put your BBQ up on the porch against a wooden railing, as it could catch fire or prevent proper ventilation.
When you've got the unit in a safe position and are ready to heat things up, always remember to open the lid of your gas barbecue before turning on the valve or attempting to light it. Letting gas build up inside the unit and then lighting it could cause burns.
If your barbecue has an automatic igniter button, use it! However, if for some reason the button isn't working (be sure to check the battery), follow the lighting instructions for your particular model. Usually, the rule of thumb is to light the grill from the side (were you wondering what those little holes in the frame were for?) and not from the top, where your face is exposed.
Another thing to keep in mind is that a cleaner grill is a safer grill. Built-up grease on the cooking area and the pan underneath can catch fire while cooking at higher temperatures (if this happens, baking soda is an effective fire extinguisher). Clean the grilling surface with a good barbecue brush when it's still hot -- before and after preparing the meal. It's advisable to remove the grease pan for cleaning when it's cool so that you don't accidentally scald yourself.
After you've got that steak to a perfect medium rare, make sure you shut off the gas valve at the tank before switching off the console. Don't close the lid until both the tank and the console have been switched off to prevent trapping any residual gas.
Always have a fire extinguisher on hand.