Before Anything Else, Clean Your Grill
You may still have food particles and grease on your grill from barbecues this last summer. Before preparation for winter, take a half hour to clean it thoroughly to prevent any dangers when turning it on next summer. Food particles could possibly catch fire or just create an unpleasant sight when turning on your grill again.
Taking Care of the Gas Line
Once your grill is clean, you need to turn the gas line off before you forget. That's important to avoid any fire hazards during the winter or next barbecue season. As far as removing the gas tubes, it's going to be up to you. Some sites say you should leave them connected through the winter. If you do remove the gas tubes, be sure to read your manual carefully to do this carefully. Every grill model is going to be different, and you don't want to cause damage to your gas line to avoid hazards.
Wrapping Up Removed Parts of Your Grill
Wrapping things in durable plastic is common when preparing things for winter. It's no different with your grill. If this is the first winter your grill will be outside, you need to wrap the burner thoroughly in a plastic bag if you're going to store it outdoors. This prevents any insects from getting into the gas tubes that could potentially cause a fire when reconnected.
As far as the gas tank, you can remove it and wrap it in plastic. You should keep it outdoors for safety due to the fire hazard of storing it in a garage or other indoor storage space. Be sure to place a protective covering over the body of the grill so that next monstrous winter storm doesn't turn your grill into a pile of rust come June.
Removing the Burner and Preparing it for Winter
You should also lift out the burner on your grill and inspect it. Furthermore, you should bring out some cooking oil and spray it on the burner to provide a protective coating so you'll avoid rust during the winter. Any other metal parts around the grill should also be sprayed to prevent the buildup of moisture.
If you're still looking for an outdoor grill to use next summer: