Some of the best articles and the links that i have found related to ATG are:

http://www.atglaunchchecklist.com/index.php?title=Main_Page

(It contains the best practices that we must follow before going into the production)

• Site perfromance can be improved by using selective cache invalidation, thumb rule is "it can be applied to item descriptor with cache mode as simple"

        for more details please refer the ATG guide ATG Content Administration Programming Guide