Septic systems utilize naturally occurring bacteria to help dissolve most material that enters the system. Common sense would tell you not to put non-biodegradable material into your system. Examples of these materials would include sanitary napkins, condoms, socks, cigarette filters, plastic, toys, cat box litter, etc. But you can also lengthen the time between pump outs by not introducing chlorine, bleach, paint, mud, dirt, or harsh chemicals like drain cleaners. These agents will defeat the system’s ability to digest and disperse waste.
Your system will not do a very good job of processing animal fat or undigested food (including coffee grounds). Consequently you should try to limit the use of your garbage disposal.