1. Area rugs should be balanced in a room. Place all of the furniture in your room either all off your rug, or all on. Having some pieces on and some off looks, well, off. I like to leave at least a foot of floor showing, even in small rooms, so the area rug remains an accent piece rather than looking like wall-to-wall carpeting.
2. When hanging a chandelier over a table, install it about 32-36" above the table surface. Too high and it looks 'lost', too low and it's not balanced in the room or functional when dining.
3. Artwork can be its own focal point, but can be grouped with furniture to create an overall vignette. I like to have odd numbers in my group, and hang pieces of similar composition, color, or with 'like' frames together. The closer you hang art in your vignette to each other, the more impact your grouping will have.
4. How large is the right cocktail table? Two-thirds the width of the sofa is always right
5. When mixing fabrics in a room, you should designate your color scheme and work within its varying hues and complementary colors. I generally select one main pattern - floral, damask, paisley, etc...- and work in smaller scale prints, stripes, plaids and tone on tone so that each fabric has a purpose and is balanced in the overall space. A good rule of thumb is to use 60% of one color in varying hues and patterns, add two equal amounts of accent hue to get 30%, then one bold or dramatic color is the remaining 10%.