[aSnakeLovinBabe]

here's how I tell the two apart:

-ribbons are much more narrow than garter snakes, they appear to be very thin and long, while garters are usually "chubby"
-ribbons are "stripey"... they have stripes and besides that, not much else in the way of a pattern.
-ribbons have a thin head, it doesn't get as wide as garters' heads do.
- if you look at the row of lip scales on a garter snakes top lip, you will notice that there are (usually) black markings in between each upper labial scale. Ribbons don't have that, they have cleanly colored labial scales.

I know there's more out there, but that's just what I go by. After a while of seeing garters and ribbons all the time, you tend to be able to tell them apart on first sight, without even realizing you are doing it.