The side of a cereal box is a good size. Take a kitchen knife and cut a square in the middle of the cardboard for whatever size photo you want. The more careful crafter can use a ruler to make sure all four cuts are even and straight.
Rip or cut out pieces of the magazine. Pick cool colors and funny phrases. I make the clippings about 2 inches long so the rolls aren't too thick. However, it's up to you how long to make yours - make them as thick or skinny as you want! The clippings can be as wide as you want the roll to be. Then simply roll up the magazine clipping like a cigarette. At the end put a little glue to keep the roll together. Then glue it to the cardboard. Just keep going until your whole surface is filled.
Note: For a more finished product, glue or tack wooden dowels to the edged of the cardboard. The frame can also be used as colorful matting and placed inside a frame.