My personal bellwether is the kitchen. It must be clean. Debris on the counter, food spills in the fridge and on the stove, pile of dirty dishes in the sink, sticky floors? No. I am not going to be comfortable staying someplace with a filthy kitchen, and I am certainly not going to eat anything that came out of said filthy kitchen.
And I say that the kitchen is the bellwether because if you (general) are comfortable with filth where you prep and eat food, then I highly doubt that your bathrooms are sparkly and the sheets on your guest bed are clean.
For myself, I have a cleaning rota where every room is cleaned (dusted, vacuumed, etc) once a week, but I do one room a day so that the chores don't lie too heavily on the weekends. The only exception to this is the kitchen, which gets cleaned daily. I don't tend to get surprise drop-in guests, but if I ever do, I am ready for them.