Share 'Joining up areas?'

Hi guys, does any one have any tips on how to join up areas over a curve so the line-up. I normally draw the art work where I "think" things will line up. print it fold it make it and the see where things are out of alignment and go back to the drawing board to make tweaks :((  I wonder if everybody works this way or if there is some other technique I should be trying! cheers RT