The following process has been fail proof for me over the years.
1. Spend some time in the area you'll be painting. Decide the feeling you want to create in the room: cool/warm/neutral, calm and quiet, light and airy, bold and dynamic, fresh and clean, etc. Having an idea of the gestalt you want to bring to the space will help you focus when you're in front of thousands of choices. Think about the feeling you want in the rest of the house as well. Whether you are looking for continuity or diversity for your house as a whole, will effect your choices. For example: a cool-toned, bold and dynamic bathroom may be a refreshing change in a house that is primarily neutral. But it might clash with a home that is solely warm in tone. These are matters of personal taste, and only you can decide whether it is appropriate for your home or not.
2. Take a trip to the local paint store, armed with the fabric, art and/or furniture stain that the paint must compliment.
3. Take samples of your safe, obvious choices . . . . . as well as shades that are lighter and darker, less and more intense in tone and shade. This is because although many paint stores use color correction bulbs above their swatches, the light in the store cannot mimic how light uniquely plays in your own home.
4. If you still have the energy for it and your eyes aren't seeing spots, play a little. What if you strayed over to the complementary (opposite) side of the color wheel? What if you picked out a tiny splotch of color found in the fabric, and what would happen if you gave it new emphasis by putting it up on the walls or trim? What if you chose analogous colors to your fabric samples? ('Analogous' meaning any three colors that are in close proximity to each other on the color wheel, i.e. dark greens/lighter greens/yellow greens/, reds/orange-reds/bright pinks, etc. For a computerized versions of a few color wheels, click on these links: http://www.realcolorwheel.com/colorwheel.htm, http://www.colormatters.com/colortheory.html.)
5. Don't buy any paint today. Take your swatches home and tape them up around the door frame to live with them for a day or so. You need at least a day to see the samples in daylight, bright sunlight, and evening lamp light. Each time of day you look at the samples, eliminate ones that don't work. Eventually you will narrow down the choices and you can feel confident that the ones that are left are the best of the best.
6. While you are choosing, glance at the rooms beyond. Do the colors work together, or will the new color create a Fun House effect? If you are changing all of those rooms eventually anyway, skip this step.)
7. If you simply cannot choose after all the above, call in someone whose opinion and style you trust.
8. Take your sample(s) with you and get your paint!
(Check back soon for 'Paint: Choosing the Right Finish')
Photo courtesy of http://www.realcolorwheel.com/colorwheel.htm.