It's as easy as ABC!
A. Design a sculpture in SketchUp
-Keep it simple
-Think about how you are going to fold and glue everything together
B. Make a 2D template
-Divide the sculpture into logical components (head, body, legs, etc.)
-"Unfold" the compontents seperately (see video below)*
-Add extra edges for glueing
-Export the 2D template (to JPEG or PDF)
C. Make the sculpture
-Print and cut out the template
-Fold and glue everything together
*I've seen some people using software that does the unfolding for you (Pepakura Designer).
That would be especially useful for complex sculptures.