What have you found works the best for best practices for user interface prototype? Customers will want to make sure their custom interface comply with ASI product standards.
Some clients won't want field level prototype screens in html like we used to do in Cold Fusion since in .net this html would largely get thrown away. The problem I see with not doing this level of prototype is that then frequently requirement are missed. Many people are visual learners and I find they don't grasp design concept until they see the interface.
Internal solution
We are using the rapid prototype product, Axure. While it does not allow you to go straight to coding, it allows you to create a prototype really fast. The app. allows you to enter specification information into each field or page. So, you can carry that information forward to implementation and actually print a design spec.
It didn't occur to me that Axure would be a benefit to consulting.