First, make sure to watch it eat before you buy. Some pet stores will tell you it eats when it doesn't or when they don't really know. This is very important in making sure it will eat fine. Next, make sure it's not too skinny. On a healthy snake, the body will make a round, circular shape while on a skinny snake, they will be more triangular shaped. Finally, check for ticks and mites. Ticks are and mites are easiest to see around the eyes and the anal opening but look over the whole body to make sure. Mites are very small black specs. They often will come off on your hand (and are harmless to humans) and can best be seen on a light area of the scales. Once you have done the above and everything is alright, then you can take your snake home!