Please read first

Links
Always post a link to your website, whether it be a new thread, a new post or just a follow on post
Always post a link with the http:// or www. prefix
Ensure that the link is to the specific page which is experiencing the problem

Screenshots
A screenshot is usually the best way to describe layout issues
If it is browser specific, post comparative screenshots between the working and non-working browsers
If applicable, add notes to the screenshot to highlight and explain the issue
Make sure the screenshot is in JPG or PNG format only...

Joomla Version
Always provide the Joomla version you are using as it dictates the solution such as 1.5.3
Try to always use the latest version of Joomla

Browser Names/Versions
State what browser is experiencing a problem
State whether it is browser specific
State the browser version, this is very important. IE could be IE6, IE7 or IE8 and all behave differently...