Need help with new designs.

I want to make some models of the Postman Pat vehicles. I want them in 1/24 scale. I do have the toy models of the vehicles that I want to build, the toys that were made for 4" tall Postman Pat figures. I can photograph the toys from all sides and reduce the images to scale, so that part can be easily done. I really don't know where to start. The vehicles are fairly simple, slab sided mostly flat surfaces. I do want to include the curves and make the models true to the series.
I guess I'm looking for tips and tutorials on making paper model patterns.