Velma Dinkley is one of the characters in the 1970s cartoon Scooby Doo. Intended to be the nerdy character with her brainy personality and thick-framed glasses, Velma has since gained a cult following and is now a very popular character to recreate in costume --- possibly more popular than Daphne, who was supposed to be the far prettier, more popular character. Making a Velma costume is quite easy as it is just clothing and glasses. A few trips to local stores will supply you with everything you need.
Don on an orange, turtleneck sweater. If you want to go for a traditional Velma, it should be a bit oversized and frumpy. If a more modern, sexy Velma is your thing, wear an orange shirt that is a bit tighter and shows more skin like the Velma in the live-action movies.
Add a maroon, pleated skirt that stops at mid-thigh.
Add a pair of orange knee-socks that match the sweater. If you cannot find a pair of orange knee-socks, get a white pair and dye them orange.
Put on a pair of maroon shoes. Ideally these should match the colour of the skirt, but any dark red will do.
Put on a reddish-brown wig with a bob style. If your hair is already the right colour and style, go with it.
Add a pair of square-rimmed nerd glasses. These can just be empty frames if you want.
Finish the costume with props such as a flashlight, magnifying glass, a book or a box of Scooby Snacks.