So take those color cards home and look at them in different shades of light. Alternately, if you want your paint to match the color of another household item, simply bring a swatch of the item's color to the paint supply store. Using a computer they can mix paint to match your color. Lastly, if you want to get creative, pick up a color wheel. Analogous colors sit next to each other on the color wheel and create visual harmony.
Complementary colors are opposite and create visual energy.
While you can't ever be certain you have the right color, keep in mind that you can always repaint. As far as brand names go, none of the professionals I talked to touted one brand over another. Most professionals emphasize the importance of a quality paint job over brands or warrantees One thing to avoid is oil paint. Nobody buys it anymore unless they have to. Latex water-based paint is the way to go.