Start at the ceiling, vacuum/clean of all dust, cobwebs, etc. around the entire room. Then start at the left or right of the door and go in a circle around the room cleaning. If there's an interruption you can SEE where you left off. Finish with the floor, vacuum/mop your way out the door.
You work in a circle and include everything in your way as you're working, whether it's pieces of art, windows, etc. Don't forget the baseboards as you are doing the floor. When you work your way out the door, then shut the door to prevent any dirt entering from other cleaning you're doing.