Is there a commonly used design specification system to present a graphic design to a customer before we start the implementation? My challenge is specifically on mailings (PDF A4, HTML sent per mail), but I am happy to hear any insight from other domains (web design, advertising, ...)
My goal is to present a document, that the customer could sign-off, and representing the actual design. Once the document is signed-off, we can start the implementation; and have very little risk that the customer is unhappy with the actual product; or request many changes afterwards.
Especially, I'm trying to avoid multiple round trips after implementation where the customer asks: "Can you move this box a bit to the left?", "Hum, can you move it a bit to the bottom?", "Can this image be a bit more blue?", "Hum, can this field be a bit larger?", "This works fine in GMail, but I'm not happy with Lotus Notes!"
I understand that iterative approaches, either billed as Time&Material, or with a capped effort, are probably better fit for that. (and if you use them, as a professional designer, please let me know too). Yet, in some projects, the customer needs a waterfall approach for some reasons. I'd like to know how to handle those cases best.