All casters must spend 1 hour to prepare their spells. What happens if a character is multi-classed with 2 casting classes and need to prepare their spells at the same time? For example: a wizard 1/cleric 2 prepares spells his spells in the morning, does he need to spend 2 hours preparing spells (1 for each class) or can he use one hour to prepare for both classes.
The GM ruled the use of a skill check, spellcraft DC 10 + cumulative caster level.
The rules don't seem to say much either way.
RAW seems to be "one hour for each". However, I don't think having seen that (and even the one-hour thing) enforced in any group I've played with.
+1 for Magicdealer's suggestion.
Or you could also consider the following points (all house-rules):
- the cleric could pray 15 minutes, then waits 45 minutes for his deity to grant him the requested spells (which would arrive one at a time)
a cleric/wizard could spend these 45 minutes reading his spellbook
- the wizard could refresh his memory of his spells, one at a time, by spending ten minutes per spell per spell level, divided by his wizard level (or any other formula you come up with)
- you could consider that, if a spellcaster is interrupted during this time, he has only memorized the first spells he chose to read/pray for