You never said, are you building from magazine plans?? If so you are going to run into a few mistakes or things the inker forgot to add or put into the drawing. What plane is it?? If the wing is constant cord and a BIG bipe I make up two hard wood templates with two holes drilled through them for bolting down the balsa ribs tight. One of the templates I counter sink the holes so I can keep it flat. I stack about 10 ribs then rough cut then gang sand the ribs then use my scroll saw or band saw to cut the spar slots. If it's a small plane or has a tapered wing then I just use the plans/template and draw the ribs onto the balsa and cut and sand them two at a time by has, just sand past the inked lines. Everything the other guys mentioned is pretty much how it is done but a lot depends on what plane you are building. I'm just finishing up my latest old school pattern plane and just cut the ribs two at a time by hand, it wasn't worth the effort to make up templates for this type of wing.