Over on the CNP Blog, I contributed a post meant specifically for our clients: a guide on how to report bugs to web developers:
Oftentimes, this process is slowed, to the frustration of everyone involved, by a lack of information about the problem. So I implore you, dear reader, to take a few minutes to familiarize yourself with the following questions and the reasons why they are important to debugging a website. If you can answer any of these, your developer will be grateful and will likely be able to make the changes faster…
The article outlines three basic requirements to any bug report: the URL where the error is occurring, which browser (or browsers) is showing the problem, and whether or not the bug is reproducible. Beyond that, there are also other suggestions that are more situational.
CNP - How to Report a Bug to a Web Developer