We have easily done over 50 Joomla upgrades over the last year. Over that time, we have developed a pretty good checklist of common problems and how to migrate most 3rd party extensions. However, those lessons were learned after knocking our heads against the wall plenty.
In an effort to save you some of that headache, here are the Top Ten Mistakes for Joomla Upgrades we have compiled. Feel free to leave comments with specific questions, as we tried to pick items that would apply to everyone.