David Musgrave has put out a great post highlighting all the Dynamics GP resources.
Personally, here is the order in which I proceed, when I need an answer -
1. Try it out in the Dynamics GP Test or Sample Company and review the Documentation
2. Knowledge Base – excellent when you have an error message
3. GP Blogs Search at GPWindow.com which aggregate thousands of articles from experts like Mark, David, Mariano and others
4. Groups Search – The public groups have a vast amount of useful data, though they are being replaced by the even better Dynamics Community Forum. I try both of them