A milkmaid costume is a relatively easy-to-create outfit of an old-fashioned dairy girl. It can be appropriate for all ages and many occasions such as Halloween costume parties, county or medieval fairs and school events. The costume can be sweet and utilitarian or short and sexy. The occasion you're wearing the costume for will determine the style and modesty of the outfit; milkmaid costumes all have the same basic elements, regardless of the overall effect.
Select a dress with sleeves to wear as the basis for the costume. Choose one with a longer, fuller skirt for a more traditional look or a shorter one for a sexier look; milkmaid dresses are usually bright and cheerful colours such as royal blue, grass green or crimson. Rolling up the sleeves if they are long makes it appear as if you've been hard at work milking the cows.
Wear a white apron over the dress; the apron can be any colour, but white will look the most traditional. Avoid aprons that have writing, pictures or logos on them.
Add a mop hat as the accessory for your head; you can buy one at a costume shop, or make one yourself with a large circle of white fabric and string. See the first resource for one idea on how to make your own hat.
Wear tights or knee socks; knee socks will look especially cute if your skirt is knee-length or shorter, but tights are good if the weather is colder.
Choose a pair of shoes that look good with the rest of the costume; almost any style will do, including mary-janes, ballet slippers, granny boots, clogs, or plain sneakers.
Place a shawl around your shoulders -- an especially good idea if the weather is colder. Grab your milking pail and you're ready!
If you can't find a mop hat and don't want to make one, you can also do your hair in the "milkmaid" braids style. See the second resource for instructions. A short-sleeved blouse tucked in to a fuller skirt is a good alternative if no suitable dress is available.