LOL....Hey, just noticed you're in Lancaster as well. Didn't think I'd see a local on here. Ok, so it's an Eastern garter, Thamnophis sirtalis sirtalis...if it's a "red one" that's a very cool snake then...possibly a erythristic or maybe a flame (don't know anyone who'd give away either of them though??????). As far as a setup, a 10 gallon aquarium would be a good start for a 12" snake, you could go up to a 20 or 30 gal. and that'd pretty much be good for life. Get a sreen lid for the top, and a heat lamp or heating pad for heat ( I like the heat lamps for gaters myself, but they do just as well with the undertank heating pads too.) Make sure you get some clips for the screen lid as well....don't want to the little buggar getting out! As far as the insides, the basics are a water dish, some hides (just something for the snake to hide in or under, one on the warm side of the tank and one on the cool side of the tank) and a floor covering ( you can use paper towles or newpaper or a lot of people use the "reptile bark" sold in stores....my fav. is the stuff called CareFresh...I use it on all my snakes). Oh, also get a thermometer so you can keep track of the temps. in the tank. It should be about 80-85 on the warm side and in the 70's on the cool side. Besides that, anything goes, there's lots of differnt pieces of drift wood, cork bark, rocks, plastic or silk plants, ect that you can add to make it up how ever you want. Also I like to have a fluorescent light on them too.....just lights up the tank nice and makes for a better looking display. You can pretty much get all this stuff at petstores, depending where you are in Lancaster....ThatFishPlace, has a good selection of stuff (I live less than 3min. from the place...some of the people there know me by name...LOL)
As far as feeding, probably the best is to get it eating frozen/thawed mice.....if it's not eating that now, you can get feeder fish (rosies or guppies, NOT goldfish) or nightcrawlers (earthworms) for now..and yes, they're both available at ThatFishPlace (I sound like an ad for the place...LOL). I would give him/her a pinkie (ie. baby mouse) once a week or if you go with fish or worms, one or two of them twice a week. Also you can hit the fish market and get fish there as well. Just watch what types you get....from all I've heard and learned, looks like trout is the best bet, and it should be available as well.
Ok, think that should about cover it!
Lastly, if you're really interested in reptiles, there's a Lancaster County Herpetology Club that meets in the North Museum every third Fri. of the month (this will be next Fri.), we have speakers from zoos, aquariums and who do research on reptiles come in and also have different events that we do and a members night when people can bring in their animals and talk about them. It's $10 a year to join, but totally free just to stop in and check things out. So again, hope the info. above helps and welcome to the wonderful world of snake keeping.
Roy