Hi Cody. Welcome.
To find garters, do like the others said and look around water, but especially, look for their food. try to find places with water- ponds, creeks, and lakes, where there are small fish, frogs, and tadpoles. Look around the whole area, especially near the waters edge.
If you can find a secluded area with water and a food source, and the weather is nice, you have a great chance of finding a garter or ribbon.