A few years ago, I took a stab at systematizing AD troubleshooting with a series of Visio flowcharts. My intent was not to have a comprehensive process to cover all AD issues, but more to have a simple guide the occasional AD troubleshooter (which suspect most IT generalists are) that you can pull out every once in a while when you have problems.
Since I put these together, Microsoft has come out with the AD Replication Status Tool, a big boost in helping you understand and resolve replication problems.
(Note: this flowchart has 13 pages -scroll down)
|Active Directory Recovery Flowchart (PDF)|
|TechNet Active Directory Jigsaw Poster (8 MB, PDF)|