What is the biggest mistake people make when dressing?
This varies with location. Here in Arizona I would say people don't venture out of their comfort zones very much. There is a distinctive 'look' that encompasses many trends thrown together, such as big patterns, bright colors, and over the top bling. It's way too much.

Also I would say that overload on the designer logos doesn't give you great style, though I will throw myself in front of a bus for a great CC or GG bag. My suggestion is to use those pieces in moderation, like wine or....wait, I never drink wine in moderation. That's a joke.

What should every women have in her closet this spring/summer?
I'm really impressed with the S/S 2011 collections, maybe that's just because I'm so in love with the 70's, and it's such a huge look. My pick is to indulge in lace, crochet or macrame items, depending on your personality and preference. It can be a dress or just a small clutch or accessory, but I'm willing to bet that this look will be a classic for years to come. It's feminine, and the texture adds that extra pop and dimension.

Who is your favorite designer?
This one is tres agonizing. The best I can do is boil it down to three: Rick Owens, Isabel Marant, and Alber Elbaz, in no particular order.