Rather than try to sell a design, I prefer to work at length with the client on the actual content and what's required to make the content most usable and understandable for the site visitors. That will help you establish a layout / wireframe. From that point, you can then dress it up as a nice design, but it's not such a big deal to "sell" the design, because the client understands it and why everything is where it is.
There are many clients who insist on having their content translated graphically first. For these clients I generally do a maximum of three rounds and state that in my contract. If they change course, then the terms have to be negotiated anew. 90% of the time, we don't make it to three concepts because almost all aspects of the site have been thoroughly discussed as the content layout has been done prior, so there remains only the aesthetic part.