Various magic users are granted additional spells when they level up.
The information just springs to mind suddenly? There is no external source, no requirement for learning the new spell?
If so, how do you guys roleplay this? For clerics I suppose its easy enough to say they are visited in a dream or something, bestown new powers for faithful service... but the other more knowledge-based mages?
It seems odd that Mushak the Wonderous can just be sitting there at the campfire with the guys and suddenly 2 new spells pop into his head.
Do we assume they are studying to gain these new spells during the current level? Are they working on their new stuff while preparing their spells for the day? Where do the new spells come from?
My working theory is that wizards (and magi, although I haven't run a game with one yet) are constantly fiddling with spell theorums and formulae in their off-time. They are the tinkerers and inventors of the magical classes, and it would be like a hobby to them. When they gain a level, a few ideas they have been working on just 'click' and they realize what they need to do to make this new spell work.
The rules assume that the character has been studying, meditating, praying, practicing, or whatever, in their off-time, much like Necroluth describes.