The order depends on the use of the sector. If for activity or work or study you look at the "facing" or water star of that sector as the host and see what the Mountain star (as guest) and/or annual star do to it. You may also look to the gua (North=1, etc) as host and see what the water /facing star does to it. So, for example, a 4-1 combo in the North will behave differently than a 4-1 combo in the South. A 8-6 combo is not the same as a 6-8 combo. A 2-1 combo in the SW might affect you but not your children even though it is no one's bedroom.
If the sector/room is for sleeping then look to the Mountain star as host.
A hill in the back of the property merely supports the mountain stars and suppresses the water stars in the back of the house. If the rooms there are bedrooms then that is perfect.
If a room includes more than 1 sector then you look at how the stars of the sectors affect each other.
Most schools more or less ignore the Base star. But some consider it the most important "guest" to look at.
If the house is not Period 8, then you look at how a Period 8 chart affects the natal chart of the house.
If there is a hill in the West (for example) then the mountain star in the west sector is supported (especially if it is the correct sort of hill). And the water star is suppressed.
But the mountain star in the NW sector is not supported unless it, too, has a hill (for example).
If there is a house in the East with a fire shape then it affects the stars in the East sector (for example). How it affects them depends on the stars there.
What the effect is can depend on which of the 24 mountains it is in.
Who it affects also depends on where this is happening.
etc., etc., etc.
