You want to depressurize your water lines by

opening one of faucets.

You open the highest facet so that no air is trapped in your waterlines. If you open lower faucets, air will be trapped in your waterline. When you turn on your main water valve, it will cause "water hammering" which is harmful to your waterlines inside your house.

If your water heater is powered by natural gas, it should have a "vacation mode". You turn your water heater to the "vacation mode" so that it won't shut off completely. The pilot light will remain on.

Best regards,

Alex