It can be a big challenge to create a design for a large object. Are there techniques or tools to simplify this, and to help estimate numbers of blocks required?
Lego Digital Designer (~140mb, Mac and PC) is quite useful for creating 3D designs. I haven't personally used it that much but it is quite a powerful tool. It will tell you the number of bricks used in a model as well.
At a pinch, MS Paint (pixel-based), Google Sketchup (find some templates for bricks) and Minecraft could even be used for planing builds.