Here is a list of various folding techniques to produce different patterns.
Spiral patterns are created by gathering a small section,usually with a clothes pin or a kitchen fork, in the middle of the fabric and slowly rotating the piece creating pleats of fabric arranged in swirls around a central point. It is then gathered into a flat round bundle and the different wedges of the circular bundle are usually dyed different colors to create a greater spiral effect.
The 'V' shape is achieved by folding a shirt in half vertically, then a line is drawn diagonally from the shoulder area down to the center fold of the shirt. The fabric is then accordingly folded along the line and bound into one or more areas to which the dye is applied. This will show in the shape of a 'V'.
The Peace Sign can be made by folding a t-shirt in half, drawing a half circle, then the center line and arm of the peace sign. The shirt is folded along the lines and tied using rubber bands. The dye is applied to form the outline of the peace sign then a lighter color is used to fill in the background colors.
(source of these techniques & pictures: Wikipedia and Google images respectively)
The easiest method is to take a trip to the craft store and buy yourself a kit and some plain white T's. (Ha, the clothing, not the band!) I think this is a fun way to spend a summer day.
Have you every made tie-dye before? If not, what are you waiting for?