In 2e it was handled with individual class rewards (which was a pain). IIRC, in 1e this was handled with gold=XP. A typical adventuring session should comprise of at least one milestone award. I generally reward an easy encounter worth of XP for minor story points and a hard encounter for major ones. This should be an significant portion of the XP rewarded. If you are going to use XP, rewarding XP for story mile stones is important. XP systems are best for sandbox style play. When running an adventure path, it is sometimes best to not use an XP system and instead just reward with levels at appropriate milestones.