Because of the high price of gasoline, how much gas do you keep in your vehicle?

I see the gasoline prices go up, then go down, then go up again. One gallon of regular unleaded is almost $3.00 a gallon. Question: how much gasoline do you keep in your vehicle? Full tank, half-full tank, fourth-full tank, or on empty? Does the fluctuating gasoline prices determine how much gasoline you can afford to buy and keep in your cars gas tank? Or, do you run on empty and say a prayer that you will make it home?