Snape wears robes that have special sleeves that flare out a lot at the arms and are split up to the shoulder.
Make the sleeves extra wide, then split each sleeve up the side after sewing your robe together.
Potion Master Jacket
black jacket that Snape wears under his robes has a high collar and
reaches down to just past his knees. The large black buttons start at
the neck and end at the bottom of his chest. There are also buttons
from the elbows to the wrists on the sleeves.
You can simulate
the potion master's jacket by turning up the collar on a black robe and
adding buttons down the front. Use safety pins to gather the robe at
your back so that it has a tighter fit. For the sleeves, add buttons
from elbow to wrist, making sure that they gather the fabric of the
robe when fastened.
Underneath the potion
master jacket, wear a white collared shirt. This should show a little
underneath the unbuttoned high collar of the jacket.
Wear a pair of black slacks, or make your own simple black drawstring pants using the tutorial available on about.com in their DIY Fashion section.
wears black square-toe boots that are usually covered by his long black
pants. This is good news for you because you won't have to worry about
what the tops of the boots look like. Find any pait of square-toe boots
at the thrift store. Apply black shoe polish if they aren't the right
Snape uses a polished black wand. It has a few inches of carvings on the helm, but the rest is smooth to the tip.
thin stick can be made into a wand. Peel off any bark and use a piece
of sandpaper to smooth down the sides of the stick. For a pointed end,
use a small knife to whittle the end of the stick. Shaving the end of
the stick should be done with adult supervision. Apply a dark or light
wood varnish to your smoothed wand.
You could also use about.com DIY Fashion's Easy Pencil Wand for kids, or one of the many wand tutorials available on Leaky Crafts in the Woodwork and Other Crafts sections, or spring for a toy Harry Potter wand.
your hair in a shaggy black cut that is parted down the middle. I
suggest smoothing a touch of mousse over the top of the hair to slick
it down and add a slightly greasy look.
Dying your hair black is
easy because all hair types will take black color well. Henna hair
color is one suggestion, because it is gentle on your hair and
typically lasts only 4-6 weeks.
This tutorial was taken with permission from about.com's DIY Fashion section.