Patterns can be either regular (see polka dot to the right) or irregular (polka dot to the left).
One woman would be very unlikely to look her best in both of these patterns – although both of them are the same shape and same color. Women who are classic types wear more regular patterns, women who are more bohemian wear more irregular patterns.
Polka dots, of course, are a rounded pattern. Houndstooth (see below) is an example of an angular pattern. Some women look good in both rounded and angular patterns, most look substantially better in one or the other and wear the other one (if at all) only if very small or muted. The angularity of the patterns that flatter most is primarily determined by your facial shape. Round faces require round patterns – the angular pattern is not harmonious.
The last thing is pattern scale. The scale of the pattern that you look best in is determined by your bone structure and height. A large boned, tall woman can wear a large print. A small boned, tall woman would be better in a medium print. Short women with fine bones wear tiny prints, short women with big bones wear medium prints. “Bones” here can mean the bones in your wrists or elbows, but I find the most telling is the way the bones in your cheekbones and nose present themselves. Are they sharp? Rounded? Full? Narrow? What shape is your chin?
Color and Pattern: Ideally, every color in the pattern you are wearing would be one of your colors. If this is not possible, the next best thing is to have at least 3/4 of the pattern you wear be your best colors, and the bit that isn’t your color away from your face. I regret to inform you that a checked print which is 50/50 white or black, unless you are a Winter, is off the list. (So is a large polka-dot print with one of those colors, or a houndstooth – and yes, I know how many prints I’ve just eliminated).