Where to find one: International Interior Design Association (iida.org) and the American Society of Interior Designers (asid.org).
Before you hire one: Sift through magazines and books, and put Post-it notes on items you like.
Common pitfalls: Going for the prestige of the name without seeing her previous work. Make sure that the quotes for furnishings include taxes and delivery charges.
They'll know you mean business when you say: “What is your markup?” In other words, will she charge you $300 for a $100 Ping-Pong table? The industry standard ranges from 15 to 30 percent, or she will buy wholesale and mark it up to the retail price.