Garter Snakes as pets
Substrates that are O.K.
Newspaper- Newspapers are cheap if not free and readily available, Take care that it does not get too wet, paper is fairly absorbent.
Paper Towels- Very similar to newspaper, an ideal substrate for monitoring a sick snake (looking for mites, colour of feces etc.)
Cage Carpet- strongly resembling felt, it looks nicer than paper towels or newspaper. It comes in a variety of colors (red, blue, green, black) and can complement your snake's coloration.
Aspen Shavings- Aspen is the safe alternative to cedar and pine shavings. It's not harmful to the respiratory tract and has a pleasant sweet smell. It's absorbant and inexpensive.
Wood Bark Chips- This really does look good in a vivarium,
very natural and of odd shapes and sizes. This can be obtained from a number
of places; pet stores often stock it, one popular brand is Reptibark.
Alfalfa Meal- This is very similar to newspaper pellet in texture and function, but is sometimes easier to find and may or may not be cheaper.
Carefresh- Carefresh and other similar products are made
from recycled paper pulp. It's soft and very absorbent. Snakes love to burrow
into carefresh. It is easy to clean and is an all around great substrate.
It does stick to food easily but that's really it's only downfall besides
it is one of the more pricey substrates.
Reptile bark- Sold under several brands, made from 100% douglas fir bark, is cleaned to be relatively dust-free, sized appropriately, resists mold, contains no irritating oils, cuts down on odor, smells nice, and looks nice but is also expensive. If you're keeping only one or a few tanks and prefer a natural look, this might be for you. Might be harmful and cause impaction if swallowed however. May be combined with coconut fiber substrate or used alone. It is sold mixed with coconut fiber and called "Forest mix" for vivarium animals. Check the ingredients to be sure.
So you found a wild garter snake
What should I do? My recommendation is to leave it alone and let it be on it's way.
If you are really interested in a pet garter snake, there are several breeders who will gladly sell you a captive bred animal.