Using the grid with room outlines, draw what the traffic pattern through the room.

Find the focal point in the room. Furniture is placed in such a way to draw attention to the focal point.
This is biggest heaviest object or item in the room.
Fireplace
Sofa
Entertainment center
Bay window or window with view
Bookcases
Build-ins etc....
 

Next consider the visual weight in the room.  Plain walls appear to be lighter in weight then ones with doors, windows etc.  Arrange the furniture in such a way that pieces don’t show dramatic shifts in height and mass as the eye sweeps the room. If a tall bookcase is next to a low desk, hang a picture above the desk for balance.   Weight of the room is important, heavy pieces of furniture should not be placed on these walls, to give the room balance. Example: Offset the fireplace on one wall with a tall bookshelf on the other wall. Do not have all big, heavy pieces at one end of the room.

People see a room like they read, left to right. 
Make sure wood pieces used together are the same wood or go with the grain not against it.
Formal and informal furniture pieces should not be placed together or near each other.
Furniture placed near each other should be the same size and scale.
Make sure vents are not blocked
Disguise what is not so attractive in the room and enhance what is.
Begin with the focal point, work clockwise around the room.

Mirrors: Pay close attention to what is reflected in the mirror when seated in the room.

Rugs: Area rugs are a valuable addition and they help define spaces and add color. Place them on hard surfaces. Keep one to two feet free around the rug. When placing a rug under a dinning table, it must leave at least two feet in each direction past the table, this will insure the chairs stay on the rug when being used. When in doubt always go size up not down.

Bookshelves:  If there are a number of shelves, use one impressive center piece placed midway down the shelves.  Use a zigzag pattern. Begin on the outside left with the highest point and then move down to shelf number two with the high point being on the right, and so on. Add interest by varying the heights of the shelves themselves. Create pockets of the same colors with books and repeat that color three times around the room. If there are two matching lamps in the room elevate one by placing a couple of books with this color under one lamp.  This elevate lamp should generally be at the left of the sofa.
 

First rule: Furniture is always placed in groupings. (Examples)
Sofa, end tables, lamps, and coffee table make one large unit or grouping.
Chair, table and lamp make one small unit or grouping.
Reading chair, ottoman, table, and light make one small unit or grouping
Bed, side tables, and table lamps make one large unit or grouping.
Dresser and mirror make one small unite or grouping
 

Groupings:
Conversation grouping indoors or outdoors: (large sofa grouping), (small chair grouping), (one single piece).
Place these groupings so the eye contact can be made by those seated and the conversation flows easily. The ideal shape is a U allowing everyone seated to be facing everyone else for intimate chatting.  L shaped conversation groupings are always uncomfortable, everyone will have to twist or shout.
Make it cozy with crowding
Make the room functional and comfortable
Two lamps: similar in height and style or matching shades.
Two identical end tables
Remember; There is always the ideal floor plan in any room.
 

Second rule: Place the largest units first, then the small units then single pieces.
Remember the traffic pattern and to give the room balance and keep the focal point.  Create a balance in the room with chairs. The colors and patterns from the drapery, plants, rugs, and furniture can help to pull the room together and give it balance.
 

Third rule: After the grouping is placed. Place the lighting in the room.
Creating a triangle with placement of lamps insuring uniformity.
Lamps used for tasks should be approx. 28" to 32" tall. Optimum height 40" to 42" from floor.
Do not place a lamp square on a table. Place toward the upholstery.
Dresser or accent lighting is 20" to 24" tall
In the dinning area chandeliers should be 1/2 the width of the table plus 9".
 

Fourth rule: WALLS and ACCESSORIES (examples)
Use good-quality paint: Inexpensive furnishings look better next to a colored wall.

Pictures: Groupings or single pictures use 2/3 of the space of the furniture it is hanging over.  Keep all picture frames uniformly the same style.  In groupings place the heavier pieces on the bottom.  Odd numbers work better clustered together.  Space all wall art about a palm's width apart, if the art is smaller than 12" X 18" then decrease the space between pictures. Make sure the art relates either by subject or color to the room grouping.

Collections: Place a collection of many small pieces on a tray. Place collections on top of the fireplace mantel or top the coffee table.
To keep a clean look in the room, limit the number of accessories.
Use the color black only as a accent.

Home Office or desk:  When placing a work desk think about the view.
Be sure to place ample lighting in the room, regardless of where the desk is located.
Analyze what you are doing most frequently and place furnishings according to those tasks.
All decorating elements apply: Remember the large and small unit placement and balance the room.
Do not place shedders, wastebasket, etc... near chairs on wheels.
Set an area for meeting with clients. (if needed).


Windows: Windows help to achieve a better balance in the room along with:
Privacy
Light
Energy efficiency
Ventilation
Views
Focal point

Mood: cozy; exciting or sleek
Use the style of the room to help with window treatments.
Contemporary
County
Elegant
Use the colors, pattern and textures in the room for deciding the window treatments.

Fifth Rule: Enjoy the room.