Green and silver are the colors of Slytherin house, and you'll need to show them off on Draco's tie, scarf and robe.
Start out with a green tie. Use silver enamel paint that you would use to paint a model car to add the lines on the tie. Fabric paint will puff up too much for this step, and the silver enamel paint will nicely soak into the tie for a more natural look. Place a ruler against your brush while you work to get the straightest lines. Make two thick lines, then skip an inch and make a very thin line. Skip another inch and repeat this pattern.
Draco wears his platinum blond locks cut straight across above the ears. This is typically known as the 'bowl cut' because it can be achieved by sticking a bowl on the top of your head and cutting right around it. For a younger Malfoy look, slick the hair back to the left side.
To be an older Malfoy, style the bangs with a just bit of gel to create a slight part at the center of the forehead, but leave the bangs to hang almost in your eyes. If you don't have the right hair color, you'll need to spring for a cheap wig or even bleach your hair.
If you have especially dark hair then it's going to be very difficult to get such a white-yellow color with any kind of hair dye. I suggest spending the ten bucks on a wig instead because bleach can be very hard on your hair.
Any 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.
Look in your local thrift stores for a white button-down shirt and a black or gray vest to wear over it.
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.
Black dress shoes will work for your feet.
This tutorial was taken with permission from about.com's DIY Fashion section.