During development, several different revisions of the theme were developed and reviewed by our client.  We made our lives easier by taking a screenshot of the site and adding notes to it, rather than trying to sum up descriptions of what needed to be changed in the body of an email.

This approach to discussion does not require expensive software, and can be accomplished using something as simple as MS Paint.  As long as a tool suits your needs, it is worth using.  So far, we’ve saved several hours worth of back-and-forth communications and clarifications because of this effective means of communication.