Start a new blank document in PowerPoint and go to File->Save As.. to save it immediately. Remember to save your work every two minutes.

OR

Download a PowerPoint graph paper template in 1/4" scale.
(control-click the above link and Save Target As....)

Click on the border of the text box that reads "Click to add title." When it is selected, use the backspace key on the keyboard to delete it.

Do the same with the "Click to add subtitle" text box. You should have an empty slide to work with.

Choose Guides -> Snap to Grid (and if desired, Snap to Shape) from the View menu.

Display the Drawing Toolbar from the View menu (if it is not already in view).

A movable Drawing Toolbar will appear on the side of the screen.

Select the line tool from the drawing toolbar and drag a line in the document to create straight walls and windows. Keep lines straight by holding down the shift key on the keyboard while you drag a line.

To change the thickness of the line, do one of two things:

1) Double-click on the line you just created. This brings up the Format Shape dialog box. Choose the Weights & Arrows tab to change the thickness of the line.

OR

2) Click once on the line you just created and then choose the Line Style tool from the drawing toolbar. Select a line thickness. For more choices, choose Line Effects.... This brings up the Format Shape dialog box.

Suggestion: Adjust the width of the line to 6 pt for walls and 3 pt for windows. Remember to draw in scale, using the top and side rulers as guides.

If you wish to change the color of the line, do one of two things:

1) Select the line you just drew and click on the Line Color tool in the drawing toolbar.

OR

2) Double-click on the line. Adjust the color (and shadow, glow, etc) using the Format Shape dialog box.

If you have been working only with the line tool, and you wish to fill in an area with color or texture (to create a floor carpet for example),

1. Select the Lines and Connectors -> Freeform tool from the drawing toolbar.
2. Click on each corner of the area you wish to fill, forming a closed shape that will be on top of the existing area.
3. Double-click on that new shape to access the Format Shape dialog box and customize the area.
   
   
   
   
4. Choose Draw-> Arrange-> Send to Back from the drawing toolbar to move the filled area behind other objects it may be covering.

After drafting the walls and windows, doors and closets to scale, add dimension lines. Try to draw the dimension lines outside of the floor plan of the room. Use a very thin line width and choose a arrow heads for the dimension line style.

Use the Text Box tool from the drawing toolbar to add text. Create a text box for the key, the scale, descriptions of furniture, and the total area of the room.

Also use text boxes in your dimension lines to show the length of the walls on the dimension lines.

Double-click on a text box to customize it.