Let them know how their life will be easier, happier, or more successful after they have bought from you. Instruct the potential customer how to buy what you sell. It costs no more to have your flier copied on colored paper, so choose a color that grabs attention but won't make your copy hard to read. Lighter colors are best. Many successful fliers have no pictures.
Line drawings are easily copied.
A photo needs to be half-toned first to give a clear photocopied reproduction. Your copy shop can prepare the photo for you. Also pay attention to the quality of the copier. Some of the newer, better maintained machines turn out photo copies that look as good as offset. The better copy shops often charge slightly more, and you may find the increase in copy quality well worth the slight increase in price.