One thing that has always helped me when doing a big cleaning job is to do it in zones. When thinking about the whole house, it can be overwhelming to the point you just want to give up before you start. Pick a specific area and clean just that area thoroughly. Maybe that's a bathroom or the kitchen or the bedroom. Get that area clean, then take a rest and do another area.

It's like the old saying. "how do you eat an elephant? One bite at a time".