A little mystery is sexier than laying everything out on a platter for anyone who has a fork.
I think a lot of it is vocal quality, eyes, and demeanor... and manners.
If you have a high voice, bring it down. Don't be giddy and giggly. Speak as if you are sure of yourself. Speak slowly (but not too slowly). Enunciate clearly. You can be a little breathy, if it's just a *little*... otherwise you sound like you're trying. Learn to use your eyes and smile to emphasize what you're saying.
For hair, either flowy, soft curls, or an updo that shows off your neck and collar bones if those are nice features.
Go for a daytime-appropriate smoky eye. Don't use heavy black shadow to get the look. Use a bronze or plum in the outer V. No shimmer. Make your eyes your focal point, not your body. Wear lipstick and liner that accentuates your lips, but be careful not to compete with the eyes. Keep your eyebrows sculpted. If your lips are nicer than your eyes, then go for a stronger lip and a neutral eye that still emphasizes the outer V. Contour your face, but don't be too obvious with it.
For clothes, go for well-structured solids that are tailored/chosen to complement your figure. Avoid animal print like the plague! Wear one statement piece, if you like jewelry. One chunky ring. Or One statement necklace. Become friends with pashminas. Use the draping to suggest curves without calling so much attention to your figure. I love skirts that are fitted through the hips and hit just below the knee. Combined with a sexy walk, they imply a bit of mystery.
Have fun with the shoes. I like pointy toes, 2.5-3-inch heel. Anything higher, and you look less confident... like you're a silly girl at a club who's trying too hard. Avoid open back shoes when you really want to pull of the look. Their noise distracts from the rest of the package.
Posture is important; slouching is not sexy. Project confidence (but not arrogance). Walk like what you are about to do is important. Walk with a bit of a longer gait, shoulders back, chin level. Keep your upper body still, but *slightly* move your shoulder forward with the opposite leg. Keep your chin level as much as is comfortable.
Learn how to sit. Keep your spine straight, but not artificially stiff. Keep your knees together. Lean your legs to the side. You can either cross your knees or your ankles.
Keep your hands groomed. Red polish says you're trying really hard. Go for clear or a neutral tone... My favs are OPI "Samoan Sand" and "Cosmo-Not Tonight Honey". French manis are a bit obvious, and nail art is out. I usually go for short, natural, square tip, buffed nails. I keep them moisturized throughout the day. I was blessed with my mother's I-could-be-a-hand-model hands, so I keep my hands simple so they don't compete with everything else. I just wear my eternity band... no bracelets or watches.
Have fun with it... And be comfortable!!! You can't pull off sexy or confident if you aren't comfortable in your body and your clothes/shoes. The point is to look at ease and confident. Nothing says un-sexy like a painful "my waistband is cutting of my circulation" or "my shoes are killing me" face.
When I was a teenager I HATED cotillion, etiquette, and elocution classes... or anything that involved being dragged to my grandmother's country club... but so much of that is useful now in business and social interactions, I'm subjecting my little ones to the same classes! :-|
