What to have ready before a mobile tech visits

Before any mobile service visit, having a few things ready saves real time on-site: know your rig's year/make/model and any relevant system brands (inverter, solar controller, etc.) if you know them, have the specific symptom description ready (when it happens, how often, anything that changes it), and clear access to whatever needs to be worked on if it's in a tight storage compartment. What are you getting looked at?