Have your septic tank serviced / pumped out / cleaned out / emptied every 2 to 3 years.
Install a low-flow shower head to save water.
Repair leaking taps.
Minimise the use of commercial cleaners and bleaches – these can interfere with the bacterial breakdown in the tank. Instead, try using baking soda, vinegar, or a mild soap solution.
Don’t flush anything down the toilet that could clog up the system, such as plastic, grease, tampons, condoms, paper towels, plastics, or cat litter. These items will quickly fill up the tank, decreasing its efficiency and making it necessary to pump out more often.
Don’t leave taps running unnecessarily, for instance when cleaning teeth.
Install a dual-flush cistern for the toilet. And by the way … sometimes it doesn't hurt to let it mellow if it's yellow. Many country households plant lime or lemon trees at an easy strolling distance from the house.