MerricB said:
G'day, Gary!
No, I can't seem to find it anywhere. (Actually, not quite true - a similar rule exists as an option in the 2E dmg!) 
The rules I can find on granting XP are:
* monster XP
* treasure XP
* special bonus for dying & being raised XP.
Were there any other class-based XP awards you use?
And just a bit back I was near to boasting of my mnemonic capacity...
Well, I certainly did hand out XPs in my campaign for spell use, also successful tracking by rangers, use of thief abilities by any PC so doing, that sort of thing.
As I left behind when I split with TSR various documents regarding a revision of the AD&D game, I wonder if perhaps amongst them I had written the information regarding XPs. Ah well, not much of a matter now anyway...
On a related topic, until recently, I thought treasure XP was awarded the same way as monster XP, that is, evenly amongst the party members. Looking through a couple of rules about henchmen made me think I was mistaken: instead XP was granted for treasure depending on how much the individual managed to acquire. Is that right?
Actually, as the DM I left it up to the players. Generally they took all treasure as property of the party, then at the conclusion of an adventure divided it in shares according to the total number of levels of the PCs involved, counting half of any multi-classed PCs levels only as addition the the higest sngle class one, i.e. a F/T/MU of 8/4/10 levels would get 4+2+10 shares of the loot.
Magic was always selected by high d% roll, each player getting a roll for each level of his or her PC--in the above example 16 rolls saving the highest. Prcks then went from highest on down. Many a tie of 00 rolls occurred. In such case the top scorerers rolled off for order of picks.
Diving into my Greyhawk books, (in reference to Tarek's query), the Foreword to the Glossography in the 1983 boxed set has a section that reads: "During Smedger's time, magic was not a lost art, but, apparently, a fading one." The foreword is signed by Steve Winter & Allen Hammack. It is even possible one of them wrote that passage.
The topic causes hotly contested debate on Greytalk whenever it turns up, much like whether the Oerth goes round the sun, or the sun goes round the Oerth.
Likely the two named individuals wrote that bit, certainly! Why they did is known only to Messrs. Winter and HAmmack, of course. "Smedgar" was Frank Mentzer.
There is no question in my mind as to the Oerth and the sun. Oerth revolves around the sun.
Gary - the Oerth isn't flat, is it? 
Oh, and thanks to RJK managing to re-release some of his modules, I'm getting an idea of how fiendish the man can be. Your poor characters have my sympathy. 
Cheers!
Oerth is a sphere, and it might be hollow...
Rob learned from me, then added all sorts of horrid nuiances and completely new devices to his store of cruel things to wreak upon PCs. As he did that, I recipriocated, and so our games were lively matters indeed. One face sharpens the other
Cheerio,
Gary