Via Digg, this post from Feministing highlights a 1943 article from Transportation Magazine. They've already seperated it out to the most ridiculous parts, so allow me to just directly quote:
1. Pick young married women. They usually have more of a sense of responsibility than their unmarried sisters, they're less likely to be flirtatious, they need the work or they wouldn't be doing it, they still have the pep and interest to work hard and to deal with the public efficiently.
2. When you have to use older women, try to get ones who have worked outside the home at some time in their lives. Older women who have never contacted the public have a hard time adapting themselves and are inclined to be cantankerous and fussy. It's always well to impress upon older women the importance of friendliness and courtesy.
3. General experience indicates that "husky" girls - those who are just a little on the heavy side - are more even tempered and efficient than their underweight sisters.
4. Retain a physician to give each woman you hire a special physical examination - one covering female conditions. This step not only protects the property against the possibilities of lawsuit, but reveals whether the employee-to-be has any female weaknesses which would make her mentally or physically unfit for the job.
More items at the original post.