[Solved] What are Effective Doctrine and Ineffective Doctrine?
Effective & Ineffective Doctrine refer to skirmishing doctrine. They are mentioned briefly in the Artillery & Skirmishing Phase section (5) and on the corresponding chart. Effective Doctrine refers to Formations which have an effective skirmishing doctrine while Ineffective Doctrine refers to Formations which would typically be considered poor or ineffective in a skirmishing competition.
In general that would be France, Great Britain, Russia in the Mid & Late War, Prussia in the Late War, and Austrian Avante Garde in the Mid & Late War. You can find out more about it in Raising an Army (one of the supplements included in The Complete Player's Guide).
Essentially it is just a question of how good they were at employing skirmishers.