Cardboard makes a fine template if you don't have plastic material available. Be sure to make several identical copies of each template and discard any that get worn down from the pressure of your pencil against the cardboard. Any flaws in the template will be carried over to your quilt pieces, making it impossible to have perfectly matching seams.
Template plastic comes in several styles. Try a few to see which works best in your situation. My favorite brand has a grid of 1/4" squares printed on it and makes marking a cutting geometric shapes a snap.