Copper based additives, made for septic tanks, kill roots that plug lines and damage leach beds. Septic tank enzymes help to liquify solids to keep the leach bed working properly.
The main thing you want to maintain is a regular enzyme treatment schedule with a product like Rid-X that will help break down the waste that is dumped into it. Also look for septic friendly soaps and toilet paper. Also choose drain openers carefully as not all of them are safe for septic tanks.
Without more information this may be difficult but I'll try. Begin by having the tank pumped out; this may solve all your problems. After that, if the tank seems full all the time, look for a water leak. If there's no leak expand the drain field and/or add another tank.
Always keep your tank pumped out. Have a drain cleaner clean the pipes leading to your septic tank. Cut down on toilet paper, sanitary napkins stuff that does not break down.