Merging households, inherited furnishings, well-intentioned gifts that miss the mark, and the occasional impulse buy (a 1950s wastebasket with bejewelled poodle . . . yes, I bought it!) -- all of these contribute to decorating dreams getting off track. (And calling it eclectic doesn't help.) Alas, you can't have it all, but you can have some of it. Here's my own recipe for getting the mix right and creating rooms that feel cohesive instead of crazy.

I call it my 80/20 rule, and it works like this: as long as 80 per cent of your interior is unified by the same style, same period or same philosophy, you can deviate with the other 20 per cent. In other words, a fine antique can absolutely work in an ultramodern space. Here are some more specifics.

Some styles just don't mix. For example, Victorian decor is all about ornate excess, while Arts and Crafts favours simplicity. Therefore, Victorian decor marries well with Edwardian, Asian, formal English, and French furniture, while Arts and Crafts is better with contemporary pieces or country styles, like Shaker. But with the 80/20 rule you can mix almost anything. Say you have a loft filled with modern classic furniture -- add a superb antique settee, et voilà. It works.

When mixing woods, consider formality: mahogany, cherry and oak are formal, so they'll go well with one another. Pine, maple, and bamboo are casual choices, which means that they're compatible with one another but less so with formal woods.

When more than one rug is required in an open space, be sure to choose carpets that harmonize rather than match. Neutral sisal may work with a faded Turkish or Kilim rug but looks too humble beside a fine Persian, for example.

In general, contemporary interiors feature 20 per cent multitone patterns and 80 per cent solid or tone-on-tone materials.

Traditional interiors tip the balance in favour of patterns. So if your family room is modern with monochromatic neutral fabrics, add some large floral-patterned pillows. Conversely, a traditional pattern-filled room requires visual breathing space, so incorporate solid expanses of colour.

Dos and don'ts of the 80/20 rule

• DO revitalize neutral interiors with punctuations of colour. A small addition of striking colour, say, a series of vases in chartreuse or a pair of pillows in cobalt, can transform the mood and personality of a room.

• DON'T rely solely on ambient or general illumination for rooms. If 80 per cent of your lighting is overhead, such as halogens or ceiling-mounted fixtures, for example, incorporate a 20 per cent ratio of decorative lighting, like sconces, table lamps, art lamps and library lights, to create interest and draw attention to collections and paintings.

• DON'T show too much leg. When mixing upholstered furniture and occasional tables, it's more attractive to vary the ratio of skirt to leg. In most cases, 20 per cent skirting (either a soft skirt like the apron of a sofa, or a piece of furniture with no legs) is ideal.

• DO save money and create a more upscale look in the bathroom or kitchen by combining 80 per cent stock cabinetry with 20 per cent semicustom or custom options. That allows you to create one standout focal feature, such as a stainless-steel medicine cabinet or a Gothic arch valance above the kitchen sink.