What processes would you use that aren't available in schools e.g die casting, would this change the materials you used?
There is also a coursework folder breakdown of what you should consider on your coursework sheets.
View a PDF document of what coursework is required from you within your project.
If your product is going to be made out of wood then mock it up in MDF.
As a general rule modelling goes Card/paper MDF (at A-level anyway - perhaps your school has access to materials other than that such as styrofoam.