Polly Singer Robert Swanigan

WHERE HAT TRENDS are concerned, big is big. Milliner Polly Singer, however, has a clever rule of thumb about how wide she'll go. "I won't make a hat so big you can't get through the door to the facilities," said Ms. Singer, the Lexington, Ky.-based designer who made her first hat in 1993, and has become the go-to resource for Kentucky Derby hats. That's no mean achievement. When it comes to the first leg of the Triple Crown, the feathery, flowery concoctions sported by female fans rival the race itself for attention. They've been an unofficial tradition since the Derby's first starting shot, at Churchill Downs in 1875.

Kentucky milliner Polly Singer shows off the classic and the trendy new styles of Triple Crown headwear. Video by WSJ's Beckey Bright.

For many an attendee, the race is a time to channel her inner Southern belle, no matter her provenance. However, the art of wearing a big hat—if you're not accustomed to doing so—can be a confusing one to master. What should women who wear glasses choose? What if you sit on it? What about hat hair? Ms. Singer and her team of four seem to have figured out how to solve every hat-related issue. Here, some helpful words of wisdom for any occasion that might call for a fantastic chapeau.

A good hat: It should complement your eye color, or make your skin look great. If you put it on and your friend laughs, it's not the one for you.

A bad hat: It's one that uses more than three colors or three styles. I've seen hats with white, orange, red and blue feathers, wrapped in tulle, crinoline and horsehair veiling.

Working the angles: I design a hat to be worn at a certain angle but I tell my customers to experiment. I made a hat for a 70-year-old, and she changed the angle and made it look Isabella Blow-ish, which was great.

On clashing: You can choose either the hat or the dress first. A strong print is really going to limit the options for a hat. I had a woman walk in [to my shop] with a crazy Missoni dress. I walked into the back room and said a prayer to the patron saint of hats.

Hair up or down? When I wear a hat, I like my hair down and natural-looking. Some put their hair in a bun or ponytail. It's really up to the person.

TO THE BRIM | A few of Polly Singer's flowery hats that would be welcome at Churchill Downs. From left: Perdita, $465, Wildfire, $345, Elle, $395, all available at Polly Singer, 859-533-1426 F. Martin Ramin for The Wall Street Journal, Styling by Anne Cardenas

Avoiding hat hair: I recommend using dry shampoo. Oscar Blandi's works for me and makes my hair feel thicker. Also, hats made of natural fibers breathe so your hair doesn't get as flat. Plastic doesn't breathe well so your hair can get wringing wet on a hot day.

Indoors, on or off? When you go to luncheon or tea, leave your hat on.

Best hat for a glasses-wearer? That's the hardest of all. A fascinator works. It's a little feather mount on a three-inch base.

How wide is too wide? The widest brims I'll make are 7 inches. The hat is 24 inches wide and comes in a monster box.

If it rains: You are out of luck! No, actually we send out plastic bags to cover hats during the race. In England, [British hat block maker] Guy Morse Brown used to make little raincoats for Ascot hats.

What men like on women: They tend to like a hat with a straight brim, cocked to one side. It's flirty. Across the board, they go for that. And, if a hat goes up at an angle, it's easier to talk on the phone.

Proper storage: To keep a hat from getting tired-looking, store it in the box so the colors won't fade. Use a blow dryer to remove the dust on a summer hat. [Holding it over] a teakettle will steam those flowers and feathers back to life.

Saving a squashed chapeau: If you sit on your hat, send it back to be reblocked.

Your unlikeliest fan? Hugh Hefner. A client was wearing one in Las Vegas and he loved it. One of his bunnies asked to borrow it. She sent it back trashed, and we said, "If this hat could talk."

—Edited from an interview by Cynthia Kling