Dress like the quintessential nerd by wearing black horn-rimmed glasses (with or without tape holding them together), a button-down shirt with a pocket and pants or a skirt that are drab or look outdated. Add an old ill-fitting cardigan to wrap up the look.
Horn-rimmed glasses are the key to a good looking nerd outfit. Add a piece of tape over the bridge or on one of the hinges, as if the tape holds the glasses together. A plain button-down shirt with a pocket, complete with pocket protector, offers a classic nerd look, or you can update the look a bit by swapping the button-down shirt for a T-shirt with a science, science fiction or comic book theme.
Wear ugly pants such as green plaid trousers that are too short, paired with white socks and brown shoes. For a more feminine look, slouchy knee highs and saddle shoes do the trick, along with an optional wool skirt in place of pants. An old-fashioned hard-sided briefcase serves as an ideal accessory to the nerd outfit. Slick your hair back if it is short; for a female version, part your hair down the middle and wear pigtails, if your hair is long enough to sport this style. Otherwise, a messy, messed up look will suffice.