I like to keep a combination of military jets, military prop.s, military vehicles, and military figures. That helps keep a nice variety. At most I have 4 at a time going. I have a shelf that can hold 4 cutting mats. On each mat I have the parts for a model, and the box with the parts I'm not using yet are on top of the shelf. That way is more efficient than just doing one at a time. When one is drying/setting, I just get another one. On the other shelves I keep reference books, and kit boxes. mostly, to decide on a kit, I just pick one on a subject that I haven't worked on in a while, like a helicopter, or a Macchi, for examaple.