How to Dress, The basics...

Here are some basic Guidelines for dressing, straight from the Mad Men website:
http://www.madmenshow.com/page/Mad+Men+Halloween+Costume+Guide

Don Draper:

Can't go wrong with the classic! Get yourself a dark suit (navy or gray), a thin tie and thin black belt, and plenty of pomade. Invest in a nice lighter and make a point of being there whenever a lady pulls out a smoke.

Hint: Study and master Don's punctuated style of handling a lighter, a cigarette, and a drink.

Betty Draper:

Grace Kelly all the way. Betty gives you lots of options: the homemaker's dress, the English riding outfit, the white nightgown, the gorgeous cocktail dress, and of course, the gone-to-the-bad- place Betty (PJs, no makeup).

Hint: You'll want to get her hair just right. (more on hair to come)

Roger Sterling:

Roger's trademarks are his three-piece suit (usually gray), silk tie, and white hair. Like Don, drinks and smokes are de rigueur. The constant leering is optional; the groping and blackface are highly inadvisable.

Hint: Change the gray suit to brown and the white hair to black, and you're Sal Romano.

Joan Holloway:

Show up as Joan, and no one will remember what anyone else was wearing! You'll need the red hair, bright red lipstick, Marilyn Monroe curves, and of course, a dress with loaded with va-voom! And learn Joan's classic walk.

Hint: Joan always wears a strong, bright color: usually red, green, blue, or purple.

Peggy Olsen:

For the girl who's just a little bit Happy Days. Start with bangs and a ponytail, then pick a stylish-but-conservative dress in more subdued colors (Peggy likes collars and plaid). A skirt- sweater-scarf combo works, too.

Hint: Have your date dress as a young Catholic priest and come as Father Gill.

Harry Crane:

Look at old photos and it's clear that more men dressed like Harry than Don in the 60s. And Harry's trademark horn-rimmed glasses and bow tie make this one of the easier Mad Men costumes to put together.

Hint: You can add a little humor to Harry by sporting a bright yellow baby bonnet as well.

Paul Kinsey:

For the Mad Man who doesn't want to wear a suit. Yes, Paul usually wears a brown suit to the office, but the office beatnik is also known for his tweed jackets, mohair sweaters, and the occasional scarf.

Hint: The two most important details are Paul's pipe and his beard. Maybe throw in a guitar.