Ways to identify/distinguish individual coyotes?

The Wikipedia entry for subspecies of coyotes has a very useful chart here (click [show]) that gives a description, range, and other information for each of the 19 subspecies of coyotes. Since I presume you are from the California area, I would focus on the descriptions of coyote subspecies that could exist around your area, such as the San Pedro Martir coyote, which has "reddish summer fur and a short, broad skull" to differentiate among the various coyotes you many encounter. Generally, the coyotes differ in color, teeth, tail size, fur, ears, and other such factors. As for determining if you've seen a coyote already, I suppose there's no real way of knowing unless there is a unique marker on the coyote's fur or appendages that differentiates itself from the others; however, examining the coyote's scats and comparing them may be a viable option for this, but that would require you to examine close to the coyotes rather than from afar.