[Thamnophis]

Hibernation is not difficult.

First you must be sure that your animals are healthy.
Make a plan about the hibernation. About how long you want the hibernation to last and when you want to start with it.
Stop feeding the snakes about ten days before you want to put them in the hibernationbox on a cold place. Leave the lights/heaters on during these ten days. In this period they can digest all the food and empty their intestines completely.

On the tenth day you can put out the lights/heaters, but leave the snakes in their terrarium. You can give them a "warm" bath before you put out the lights/heaters. This to help them get rid of their last faeces.

Put the snakes one or two days later in the hibernationbox and make sure that they cannot get out of it. Also make sure there is some ventilation.
As a substrate you can use ground, leaves, sawdust, woodchips, etc.
This substrate has to be kept a little bit moist.
Personally I have never placed a bowl of drinkingwater in the boxes, buit some people do. I have never lost an animal during hibernation.
Check the box once a week. Is it moist enough? Is there mold in the box? Is it cold enough?
I put an old (but clean) towel on top of the sawdust that I use. This I keep moist.
Temperatures may not get lower that about 4°Celsius to be save. Best temperature is between 4 and 10 °Celsius, but this is also dependant of the species that you want to hibernate.

Hope you understand my limited knowledge of the English language.