AD&D is quirky system. It works, but it begs to be house rules like this predecessor.
Dungeon Masters new to the game should consider the following questions before attempting to run it.
1. Which books will you use?
You can have a perfectly fine game just with the Players Handbook, Dungeon Masters Guide, and the Monster Manual.
In fact, players new to the game should just stick to these. Save the additional rules found in books like Unearthed Arcana and the Dungeoneer’s Survival Guide until you grasp the basic rules.
(Okay, fine, Dungeon Masters are allowed to use monsters from the Fiend Folio…)
2. Do you understand the combat system?
AD&D uses combat tables to determine hit probabilities. The same goes for saving throws.
The initiative system is based on 1 minute combat rounds divided into 6-second “segments.”
The detailed rules and charts for this are found in the Dungeon Master’s Guide, not the Player’s Handbook. So expect a lot of questions from your players.
Hint: Being surprised is very bad–especially if you’re a spellcaster.
2a. Will you use weapon-types vs. armor class?
In a low-magic campaign these bonuses make sense. If so, your character should proficient in the all mighty flail.
3. Do you understand movement and distances?
AD&D switches back and forth between inches and feet, which can get a bit confusing. Inches represent distance on the tabletop, as in a wargame. And it get’s better: in the dungeon or inside a building, 1 inch = 10 feet; if outdoors, 1 inch = 10 yards.
4. Will you use miniatures?
Using miniatures will change the ratios for movement. Back then, miniatures were smaller, but two “true 25mm” miniature still won’t fit inside an inch.
5. Can fighter/magic-users wear armor?
The same goes with the cleric/magic-users. The rules pretty much say “yes” (though not an explicit “yes.”) But many Dungeon Masters over the years have said, “no.”
6. Will “demi-humans” have level limits?
Elves, dwarves, halfings, etc, where given level limits to compensate for their racial abilities. (That is, few players would want to play a human)
So, you want to play a half-elf cleric? Well, you can only go as high as 5th level. Even elves without high Intelligence are limited to becoming 11th level wizards. It’s why demi-humans can multi-class (but will advance in levels really slow).
7. Are Bards allowed?
Ah, the original “prestige” class. You probably won’t have to deal with this question because most campaign don’t last long enough for Bards to come into play, anyway.
8. Are psionics allowed?
Now psionics are a game-changer. Even though the chances of a character possessing these abilities are very slim, you could end up with a character with Astral Projection. Allow the with caution.
9. What method will you use to generate ability scores?
The standard method is 4d6 and drop the lowest. But that’s not in the Player’s Handbook, it’s in the Dungeon Master’s Guide.
10. Will you suspend everything you know about later editions of D&D?
Except for maybe AD&D Second Edition.
The reality is Advanced Dungeons & Dragon is different game from its successor. You should learn it without any presumptions.