Be unique :)
Firstly, get everything you need to dye clothing: a bucket/tub, fill it with water, and follow the instructions for the dye.
When the dye is ready, dip the sleeves into the tub and let sit for as long as the instructions say.
The dye should creep up the sleeves, giving them a very cool look.
Wash. The dye will dye the hoodie a slightly darker shade (I started out with a white hoodie).
Cut out pieces in the shape of the front pockets and the back.
Sew the pieces to the hoodie, using a zig-zag.
And voila! Your punk hoodie is done.