Lingerie connoisseur Rebecca Apsan has been selling some of the sexiest underwear in her downtown Manhattan boutique, La Petite Coquette, for nearly 30 years.

After decades of experience dressing clientele that includes celebrities, models, and even the Sex and the City gals, Apsan has compiled her tried-and-true tips in one book.

Drawing on her knowledge as the "best bra-fitter" in the U.S., "The Lingerie Handbook" (Workman Publishing Company) is a tops-to-bottoms guide on once-unmentionables such as bras, panties, slips, stockings, teddies and camisoles. You name it, she mentions it.

Not only does she offer straight-up advice on what were once considered unmentionables, she breaks taboos and helps women find their inner sex goddess.

Apsan, who recently launched her own line of lingerie on QVC, says intimate apparel should never be relegated to the bottom of the hamper. Top-drawer underwear has a transformative effect, she says.

In a one-on-one interview with CTV.ca's Mary Nersessian, Apsan bares not only her trade secrets but divulges her A-list celebrity clientele.

Mary Nersessian: How did your love story with lingerie begin?

Rebecca Apsan: When I was a child, my mother always wore beautiful lingerie, I remember brushing up against her and always feeling this silky feeling -- so I could never get that out of my mind.

She always bathed us three sisters in sweet scents, dressed us in pretty little nightgowns. That's where the love affair with lingerie started.

M. N.: When did you open the store?

R.A.: In 1978. I was very tired with my second husband who had a habit of ripping off my lingerie in a heat of passion, so he thought it would be cheaper to set me up and he lent me the money to open my own shop.

M.N.: Have you been at the same location since?

R.A.: I started off right across the street, at a 160-square foot space -- it was about the size of a closet. I just wanted to fill it with the most beautiful and sensual lingerie that I could find, I attracted a lot of models, editors, and actresses and soon it was a word-of-mouth success. The rest is history. I had no idea it would become as big as it would.

M.N.: What is a coquette exactly?

R.A.: A little flirt, a pampered woman -- someone who likes to take care of herself in the best way possible.

M.N.: How have you seen your clientele evolve over the years?

R.A.: More women are realizing how important their undergarments are.

M.N.: What's so important about the right undergarments?

R.A.: This book is not about bra-fitting, it's about taking care of yourself, because undergarments are really foundation undergarments for how outer clothing looks on you. I'm very tired of looking at women with visible panty lines and ill-fitting bras, which can definitely ruin an outfit.

By putting women in the right type of lingerie, there is a transformative power that takes place in people. I get stopped in the streets all time, and people tell me "You're responsible for this child" or "You're responsible for me feeling so much better.

There are four words I've heard my entire life: "You've changed my life," and that makes me feel very good.

M.N.: In your book, you say that you not only work as the owner of a lingerie store, but as a therapist, how so?

R.A.: As soon women take off their clothing, they feel vulnerable, and you cannot believe what is revealed.

A lot of women talk about cheating on their husband, or reveal that they don't have a sex life, or say they are looking to bring newness into their lives.

M.N.: How does lingerie have the power to bring newness into your life, or not only to change your look, but your outlook, as you say in your book?

R.A.: When your bra and your thong or panties look good, you feel good when you put your clothes on.

You feel good especially when you are feeling pretty. When you wear the wrong-sized bra or your panties are rolling up, you will be fidgeting. When everything feels good, everything else will fall into place.

When I wear silk underwear, I walk differently and I talk differently because it feels good against my body.

Sometimes women who are wearing $7,000 Chanel suits walk into my store, and they are wearing ripped underwear. They say, "Who's going to see it?" A lot of women really don't care about their underwear.

M.N.: What does that say about them?

R.A.: It tells people they only care about what's on the inside.

M.N.: What was it like providing some of the intimate apparel for the "Sex and the City" television show?

R.A.: The most exciting part was when they wrote us into the script. In one of the episodes, Samantha Jones (Kim Catrall) receives lingerie from Richard (James Remar). She opens it up, and says "La Petite Coquette, my favourite."

M.N.: What are the main mistakes women make?

R.A.: I don't think women spend enough money on their bras and underwear. When you are wearing a decent bra, it fits you better and it will last longer.

M.N.: How about a woman who feels she is too curvy to pull off the look of lingerie?

R.A.: I think that a lot of women feel that they don't have beautiful bodies and don't feel they should wear lingerie, they think they are not worthy of it.

I'm not going to give her something that reveals her body completely. I'll give her a beautiful gown, a nice robe to put on top, a gorgeous bra and panties set. Most women who have D-cups don't realize there is a selection, they just have to find it.

M.N.: What are some of your least favourite trends that have come and gone?

R.A.: I really don't like the trend of seeing lingerie worn outside the clothes. If you show everything, there is nothing to be left to the imagination. When you show a man a little bit of lace peeking through your shirt -- that is sexy. But the thong outside of the jeans? I hate it.

M.N.: What's the latest trend that's catching on?

R.A.: We're seeing a lot of boy shorts, not in place of thongs necessarily, but they are going neck-and-neck. I am also seeing a lot embellishment because of the film "Marie Antoinette" - there are lots of corsets to be worn out, a lot of beautiful laces.

M.N.: Can you tell me about your celebrity clientele?

R.A.: I can't tell you what they bought.

M.N.: Then tell me who you've sold to.

R.A.: Britney Spears has been in, J-Lo, Salma Hayek, Julianne Moore, Natasha Richardson, Ellen Barkin, and Liv Tyler comes in a lot. Keith Richardson from the Rolling Stones also comes in for his wife... and Cindy Crawford is a wonderful customer.

M.N.: Tell me, do their under-clothes personas live up to their public ones?

R.A.: Absolutely. They are the same under their clothes. But I will tell you they wear shapewear to suck them in. What do you think they are wearing on the red carpet? This is why I wrote the book, so that not only A-list celebrities can look like that.

Celebrities on the red carpet are wearing chicken cutlets to make their cleavage a little better and wearing shapewear to suck themselves in.

M.N.: What are you wearing right now?

R.A.: I am wearing a very, very sexy turquoise bra with lace coming through it and a turquoise thong. I chose it because I was wearing a black sweat suit, and it was boring so I wanted to liven it up a bit, and I wanted to be happy on the plane. Like I've always said, a good bra is a like the perfect man: good looking, supportive and will never let you down.

M.N.: The difference is, you can buy the bra.

R.A.: Right. You can't buy the man, unless you are very, very wealthy and he is willing to be bought.