look on the internet for overhead shots of a firebase and see how it is set up, then determin where and what you want the scene to be of (what meaning is there a gun being loaded and fired, or just an r&r scene) next get the models and build them up real nice. If they dont turn out how you want them, then redo them until they do. once the models are how you want them, then determine the size of the base and all that. once you got the right size base, then get all the materials you might need and with out actually using the materials, plan out how you want the scene to look using you imagination to make the ground in your mind. once you got that then just build away