A perfectly-lit bedside table by Ashley Whittaker.

1. Relying on Only One Light Source

The key to good lighting is layering it at different heights. "Don't rely on only one kind of light source. Mix a variety of overhead and floor or table lamps," Alan Tanksley says. "Warm 'pools' of light draw people in and create intimacy."

2. Using Overhead Lighting That's Too Bright

"There's nothing worse than bright lights that make you feel like you're onstage," says Barclay Butera says. He recommends using dimmers and soft white bulbs in every room, including bathrooms. "Lighting shouldn't wash down on you: It's harsh and unflattering."

3. Not Thinking About Wattage

"Mood is everything, and who wants to dine in bright light? 60 watts for the dining room," Barbara Barry says. "I want it bright when reading, so 75 to 100 watts for the living room. It's nice to have options — if you don't have dimmers, then have some variety from 40 to 100 watts, so you can change the mood for the occasion. The bathroom needs overhead as well as side lighting. Keep the overhead to 75 watts, with 60 watts on each side. The best lighting is at eye level, not overhead, which creates shadows. And the best light is diffused light from a white or off-white lampshade."

4. Going Overboard With Recessed Lighting

"Use recessed lighting sparingly. Too many fixtures turn your ceiling into Swiss cheese!" Anthony Baratta says. And be mindful of where you place that kind of lighting. "Limit overhead can lighting to functional areas such as bathrooms and laundry rooms — the light is too harsh and flat for your living areas," Timothy Corrigan says.

5. Forgetting About Dimmers

"Lighting is everything. It creates atmosphere, drama and intrigue in a room. The easiest way to accomplish this is with a dimmer switch. I always use dimmers, even in the powder room!" Martyn Lawrence Bullard says.

6. Light Switches Placed in the Wrong Place

"We locate light switches about 36 inches above the floor. That way they stay out of the way of the art on our walls. We put switches about 1½ to 2 inches off the side of the door casing for the same reason," Gil Shafer says.

7. Neglecting Your Closet

Your closet needs attention, too. "Some good, solid recessed lighting is clearly going to help to distinguish this pair of black trousers from that pair of black trousers!" Scot Meacham Wood says. "We will also regularly add a gallery fixture across the header of built-in closets as a secondary light source. You're regularly working with matching colors and textures while getting dressed each morning, so having good lighting is a requirement."