I have not seen much about what material people are using for templates so I though I would throw out what I do and see what other ideas people have some up with. Sorry if this has been discussed before.
I started using cardboard, like what are on the back of a spiral ring notebook. These were not very durable so I was thinking about using something else. I thought about metal but it seemed like over kill. I came up with a plastic that works great. It is the plastic from a yogurt container lid. It is flat, a good thickness and much more durable than cardboard and easy to cut with scissors. You could use a butter container lid or cottage cheese lid and so on.
what i have always done is to print them out (i make templates in photoshop) on normal printer paper, then i use that 2 inch wide clear packing tape to 'laminate' them before i cut em out. i also made a set using a business card and the lamination technique.