If you are performing a play set in certain period, become familiar with the clothing of the period. For example, if you are making costumes for "The Importance of Being Earnest," which first premiered in the 1890s, visit sites such as Costumer's Manifesto or Fashion Era to look at images of clothing from that period. If you are costuming Shakespeare's "The Tempest," study fashions from the 1500s by going to sites such as Costumer's Manifesto. Becoming familiar with the period in which the play is set helps you create your costume design. Books are also a great resource, such as Janet Arnold's "Patterns of Fashion 2, Englishwomen's Dresses and their Fashions C. 1860-1940" as well as "A History of Costume" by Carl Kohler (see Resources).
Draw a fashion silhouette to help give your design the proper look. These silhouettes vary from era to era. Sites such as Fashion Era offer fashion silhouettes for each period.
Use paper that is semi-opaque when you are drawing your costume designs. It will allow you to see a illustration beneath the paper to establish the lines of your drawing.
Softer pencils work well when drawing costume designs. A 2B pencil is helpful when you are sketching. A 4B pencil---which is a little harder---works well for adding emphasis and highlighting. Use a rubber eraser; it doesn't rub away layers of the paper.