Start by getting the system located and the record pulled, since most counties around here keep the original permit and as-built on file and it saves a lot of digging. After that, an inspection plus a pump-out gives you a baseline and puts you back on the books. Washington does have ongoing operation and maintenance expectations depending on your system type, so it's worth confirming which category yours falls into. We used Septic Solutions for our septic services and they handled the paperwork side, including the disposal manifest. Also ask them to install risers if the lids are buried, it makes every future visit cheaper.