Pursuing the abstract procedure itself for deconstructing any given 3-dimensional geometric solid into its corresponding 2-dimensional net is perhaps not the optimal place to begin.  Partially extending upon the links that Ian provided above, I suggest that starting with previously established 2D nets so as to copy and then construct them into 3D solids (and then deconstruct them back into 2D nets) might provide an easier demonstration of the concept.  With that in mind, here is a listing of 65 geometric nets , each of which has a downloadable and printable PDF file.  (If you do not already have a PDF viewer installed on your computer, I might recommend SumatraPDF if your operating system is Windows.)