Using the basic plan, take everything off the windows and clean them.
Take everything off the walls and clean items and wall.
Empty all drawers, shelves, ledges, etc. Clean items, but don't replace-- YET.
Using the philosophy from the "It's Here Somewhere" decide what you want to use this area for: eating, entertaining, playing games, alternative office space, etc.
Then place only those items related to those uses back into drawers, shelves, whatever.
Declutter! Use the 4 box method, place everything that isn't useable in this room into the appropriate box. trash, Goodwill, someplace else or storage.
Streamline down to what you will actually use in this room.
Remove all furniture, and clean the floors and baseboards.
As furniture is replaced, clean each piece with appropriate cleaner/wax. Check chair/table legs to see if they need new protective caps.
Re hang pictures. on the wall -- only try using only half of them. Then add more only if you can't stand the empty look.
According to the "Law of Household Reduction", when you decrease the number of things, you expand your space visually as well as physically.
Add a new arrangement or fresh flowers and plan to invite company for dinner!