Buy inexpensive plain masks, either whole- or half-masks, from any crafts store. If you buy the slick plastic masks, you will need to cover them with fabric so that the decorations will adhere. The technique is below. The mask forms that have a nylon base can be glued to directly.

Tools:
Elmer's Glue and/or Low-Temperature Glue Gun (with colored glues for special effects like blood)
Small paint brushes or popsicle sticks for each person

Supplies:
1 or 2 masks per person
An assortment of small items that can be glued onto the masks such as:
sequins, fake jewels, dried noodles of different shapes, feathers, beads, plastic or dried flowers, fern leaves, dried leaves, plastic glow-in-the-dark insects like cockroaches, worms, snakes and other creepy crawly critters, glitter, ribbons
Fabric for the base such as brocade, camo fabric, etc.

Spread an old sheet or table cloth over your table - this gets very messy. Pour a small amount of glue in disposable bowls and give one to each mask maker. Each mask maker also gets a popsicle stick or paint brush.

If you are using fabric as a base for the mask, spread the glue thinly over the front of the mask and mold the fabric to the form. Let dry. Carefully cut out the eyeholes and trim close to the eye edge of the mask.

Start applying the decorations at the center of the forehead area and work out so you do not mess up what you have finished. Feathers and other decorations that are a bit heavy need to be attached with the glue gun.

Scary effects can be made with the colored glues that can be purchased with the glue gun.

Let dry completely before wearing.

If the mask doesn't come with an elastic band, attach after dry. Or you can use ribbons that match the mask.

More resources for mask making can be found at: http://www.microsoft.com/athome/morefun/createmasks.mspx http://familyeducation.com/printables/package/0,2358,22-9732,00.html
About the Author

Victoria has been sewing and crafting for over 15 years sewing gowns for SCA events, costume balls, weddings and the theater. She began making masks to match her own costumes. She now sells these custom masks at fairs and online at Custom-Masks.com