Gas Billing

How is gas charged out on my bill?
I am moving into a home that we just purchased. What am I supposed to do?
I am moving into a rental property. What do I need to do?
I am moving out of my place, do you need to shut off the gas?
I have a gas stove - if there is a power outage, can I use the stove as an alternative heat source?
Why do we have to pay our bill by the 25th of the month, but we can't give our gas reading at the same time?