The answer to 'how to maintain septic tank' is to regularly inspect and service your septic system. This includes having the septic tank pumped every 3-5 years, depending on the size of your household and usage. You should also avoid flushing non-biodegradable items down the drain, and be mindful of what goes into the system to prevent clogs and backups.
Regular maintenance helps extend the life of your septic system and prevents costly repairs. It's also important to know the location of your septic tank and drain field, and avoid driving or building over them, which can damage the system.