The French Linguistics site has an overview of the position of French adjectives that will hopefully get you started. Any suggested improvements/clarifications or contradictions to this material would be welcome.
At a beginner/intermediate level, you can do pretty well by taking the view that the usual position for the adjective is after the noun, and then learning a few adjectives that pretty much always come before (see the aforementioned page). It's also worth tackling the question the other way round, and considering adjectives that basically always come after the noun (again, the page lists common cases).
But you're right that it's quite a complex issue, and certainly could lead to some interesting discussions here.