Well, I posted a thread on this subject over at Canonfire! In a search for various methods used by DMs. I discovered that we all do it pretty much the same, except for some minor differences. Now, as promised, I deliver my thoughts on the subject.
The chart (Table 4: Intelligence) on page 16 of the 2nd Edition Player's Handbook provides an excellent guideline. Reading everyone's post on Canonfire! shows that we all make our "minor" adjustments. I agree with some that were mentioned, but disagree with others. All will be "laid out" here. My "discussion" will try to follow the comments from Canonfire! as they occurred in the actual thread.
First, the 35% chance of learning a spell, that's for an "average" Intelligence score of "9." The percentage chance of learning a spell goes up as Intelligence goes up. We all apply the 35% as is intended in real life mathematics. I think that this percentage progression is fair. I do – however – require them to have rest and be in a "quiet" place . . . at least "in camp," in relative "safety," so that they might be undisturbed.
There are a few who disagree with the percentages outlined above, at least when it comes to how many spell levels a Magician can learn based upon his/her Intelligence score. I agree with the thought that Intelligence should not play a part in how many spells a Magician can know, that is, how many spells he/she might have in their spell book. But I think Intelligence should limit the spell levels a Magician can learn.
Remember that an Intelligence score of "9" represents and "average" Intelligence. The truth is that, in real life, the vast majority of people with an "average" Intelligence are never going to earn their Ph.D. For the most part, they find the work "too hard" and are not willing to put forth the necessary effort. I think that should apply in the game as well. If you want your Magician to gain his /her Master's or Ph.D. in magic, then he/she needs the necessary Intelligence score to do so.
In comparison, take the Fighter; the average Intelligence score is perfectly acceptable, it makes them capable of learning "the basics." But to be a superior swordsman, the Fighter needs "more," he/she needs the Strength and reflexes – or Dexterity – to reach the higher levels of skill.
Another example is the Cleric. To perform his/her "miracles" – cast spells – the Cleric needs Faith. On several occasions Jesus told his apostles that they failed because they lacked Faith. In the game, Wisdom – rather than Charisma – best reflects Faith. So the Cleric, too, can get by with "average" Intelligence.
The Magician, on the other hand, has no real need of Strength, Dexterity, or Wisdom. For the Magician, everything hinges upon his/her Intelligence score. This makes the Intelligence score vital for the Magician and this is reflected in the Magician's ability to learn spells and attain spell levels. But we have to bear in mind that Intelligence is a dynamic and fluid quantity. I try to "reflect" this quality in rerolling the failed attempt for learning a new spell. I do not make my player wait until he/she attains the next PC level before attempting to learn the spell again. I do require them to wait a certain amount of time, which is, itself, reflected in waiting until our next gaming session. Basically, they need to return to their "safe haven" – perhaps the Green Dragon Inn, or some such – and "rest and reflect" for a period of time. I then permit them to reroll the attempt.
In response to the "automatically learn" reply, I say . . . no, not really – depending upon the spell. For instance, my Magician is 5th level and he/she "discovers" a couple of 1st level spells that he/she did not previously know. Those are a "given." They're "freebies," sure. For 2nd level spells, I require them to roll, but . . . I acknowledge their experience – by increasing their chances of learning the new spell. Experience should not be "over looked" when determining the percentage chance of learning a new spell. Training is one thing, experience is another.
But, if my 5th level Magician found a "new" 3rd level spell, well, that requires him/her to make their percentage roll and they must meet the criteria as set above – a quiet, contemplative place, where they will not be disturbed. Naturally, as they progress to the point where they know and are casting 4th and 5th level spells, then learning 2nd level spells becomes automatic, and so forth.
Also, I require them to "find" new spells – scrolls they discover, spell books they find, returning to their school or Mentor to acquire a new spell, etcetera. I do not allow them to automatically know a new spell. Now, I do allow one exception to this rule; when they are 1st level, I roll one d6: roll 1-3 and they have one 2nd level spell in their book, roll 4-6 and they have two 2nd level spells in their book. These spells reflect a "gift" from their Mentor – or Academy Teacher – who may have been fond of them. Thus, when they reach 3rd level in the middle of a Dungeon – once they "rest" – they will have a chance to know one or two 2nd level spells. But that ends the "freebies."
Controlling this aspect falls to the DM. As I've said before, I require my players to provide me with an equipment list, NOT for weight – I don't bother with encumbrance – but for availability.
DM: "So, how are you going to get down there?"
PC: "I'm going to tie a rope to . . ."
DM: "Stop! Do you have a rope?"
So, does your Magician have the necessary spell components? Or did he use them all the last time he cast that spell? Hmm? The DM needs to keep/have a copy of the equipment list and check off each item that gets used when the PC says he uses it. For instance, after they climbed down that last cliff face, did anyone bother to retrieve the rope? No? Well then, they're going to tie off what rope?
I do not assume anything, speak the words . . . or you didn't do it!
It also takes time to memorize the spells. I include this in rest periods, but, the higher – more complicated – the spell, the more time and "quiet" the Magician needs. Resting in a Dungeon may find my Magician going into battle without his/her 5th and 6th level spells. It all depends; did they get enough rest and undisturbed meditation time?
I determine this by rolling dice. But I allow each roll to represent four hours. In other words, they lay down to rest, "four hours" later, I roll a dice. Is their rest interrupted? I do it again at the end of eight hours, to see if "they" will be interrupted while the Magician is trying to meditate. Once they are "awake," then each roll represents one hour. In this way, if they make the first two "four hour" rolls, the chances are good that the Magician will get to rememorize some spells, but maybe not all.
And though I've mentioned "rest," let's elaborate on it a bit more. Using powerful magics – 8th and 9th level spells – is supposed to be very taxing mentally and on one's physical strength as well. So I require eight hours of sleep, then they can meditate upon the spells they wish to learn.
As a former Over-the-Road Truck Driver, let me assure you that the Department of Transportation drives us "nuts," continually hammering the facts at us. What facts? Full Grown Adults require 8 hours of uninterrupted sleep to function at 100% . . . children require more.
"But Mystic, I only need 6 hours of sleep!"
Yeah? Razzberry! You're talking to a guy who has been forced to read ALL the material, it is required by LAW and you WILL be tested. Doctors and Scientist disagree with you. You are not "special." You require 8 hours of sleep, or you're not "functioning" properly.
I require this of my Magicians, persons who wish to engage in a mentally taxing enterprise. After getting the needed rest, they may meditate on their spells. I do not wish to bog down the game with extreme requirements, however, so I require no more than half an hour for each 8th and 9th level spell they wish to memorize. A quarter of an hour for 5th to 7th level spells. Five minutes for the "lower" spells. Their adventuring companions will simply have to wait, or delve deeper into the Dungeon without the "high powered" spells. Good luck!
Alright, this is getting long, so we'll have to continue this discussion in another post. Next time, look to read about the 2nd Edition's Complete Wizard Handbook kits. See you then!