To begin making a diorama, think about the diorama's theme and the materials available. Some themes are too broad to fit into a small frame, while others don't require much space. Once you have sketched out the idea, build the diorama, working out from the background and up from the ground.
Gather materials before building the diorama, so that everything is easily accessible in one place. Cardboard, paper, twigs and glue are all versatile and inexpensive. Papier mache, paint, modelling clay and even collage create striking backgrounds. If a lot of mountains are part of the scene, try using painted Styrofoam for texture.
When adding details to the scene, work from the back and sides towards the center. Then, once all the main elements are in place, work on adding details and extra figures.
Glue sand, gravel or soil to the diorama's base to create a realistic outdoor surface. If the diorama is of an indoor scene, consider printing out photographs of wood floors and gluing them down. Twigs and small sticks make excellent trees, especially if the theme is related to winter. Glass, cellophane and nail polish are good substitutes for water.
Adding detail to the sky is a finishing touch; use glitter to represent stars, or make clouds out of cotton balls.