Make sure you turn of the power to your pump and locate the pressure switch. It will probably have some kind of plastic or metal cover on it that you will need to remove. Make sure you put the switch cover somewhere it won't get damaged. If your pump isn't operating as it should be pry back the switch relays and inspect it for damage such as pitting or burning. Clean the contacts and perform any pressure adjustments you feel is necessary.
Cleaning the Contacts
To clean the pressure switch contacts, slide a length of cloth between them and pull the cloth along them several times. Repeat this on the other side until shiny. You can also unscrew the aerator in order to clean the smaller parts or replace it if damaged.
Adjusting the switch
If you need to adjust the switch then you should know that pressure switches are in conjunction with pressure gauges and these are set to turn on at low pressure and off at high pressure. Adjustment instructions are normally on the inside of the switch cover and you will probably need a wrench to turn the adjustment screws but make sure you follow the manufacturer's instructions.
Performing these steps every so often can help extend the life of your water pump and save you money in costly repairs.