Next to paint and lighting, there are few decor items that have as strong or as instant an impact as a good area rug. They define zones, add color, pattern, and texture, and lend a room that often elusive sense of "feeling finished." And in neutral rooms — all you banned painters take heart! — all it takes is a bold rug to set the tone.

It took me quite a while to realize just how significant a role rugs can play. They are by no means the least costly part of a room — and since they're not always as necessary as say, a sofa — they haven't always topped my priority list … until now. Some of my favorite Apartment Therapy House Tours have convinced me of their crucial role, especially when painting is not allowed or a bold wall color is not desired.

When the majority of the room is neutral, an eye-catching rug, whether bold in color or pattern, can set the rock and roll vibe or be the something "off" that makes a room feel interesting and a little unexpected. The best examples are the ones where the rug doesn't necessarily match, which is one reason why richly colored oriental rugs have long been a favorite in home decor despite the ornamentation in the rest of the room.

Before you make the investment there are a few basics to take keep in mind:

• Make sure the rug is big enough.Obvious, right? Well, I've learned the hard way (twice) that purchasing a rug by sight rather than by measurement is a huge mistake. Rugs in a showroom or store can appear deceptively large, only to feel more like a bathmat when brought home. So measure, measure, measure and save yourself the trouble.

• The two leg rule. In the past, the rule of thumb was that all four legs of a sofa or chair should be on the area rug, but nowadays its common and even stylish to have just the front two. Anything smaller loses the effect and can make a room appear wimpy or out of proportion.

• Play up the rug color with other similarly colored accessories. This is not always necessary, but in a neutral room, any loud color shines…sometimes to the point of feeling jarring. To soften the effect or make a room feel more balanced, pick up a color from the rug through other accessories used around the room such as picture frames, artwork, or vases.

Images: 1: Apartment Therapy New York: Carl and Laurent's Bright White Live/Work Loft, 2: Leah Moss, 3: Style At Home, 4: Apartment Therapy DC: Caroline's Pint Size Retro Whimsy On A Budget, 5: Apartment Therapy DC: Allison's Playful Chinoiserie Modern, 6: Cottage Living, 7:Apartment Therapy DC: Stefan's Inspired and Eclectic Studio, 8: Apartment Therapy LA: Jason & Denise's Warm & Bright Ranch