Gary provides tables for generating followers for PCs who have reached "certain levels" and done "certain things." The closest thing I've ever seen to these tables and rules, which take up about two pages (and Gary fits a LOT on one page), is the ACKS rules, but the ACKS rules are much, much more streamlined than these tables; the way I see it, ACKS creates a much easier-to-use framework, but the DMG provides more variety and, in some cases, more detail, and I'll probably incorporate large portions of it into an ACKS framework if I ever run games where PCs begin establishing strongholds.
Let's talk about Rangers first because, frankly, while the other tables are very cool, they pale in comparison to the tables for generating a Ranger's followers. Rangers get 2d12 followers, and the fewer followers they get, they cooler they'll be, as each result on the 2d12 comes with a modifier for the d% table you roll on next; for example, if you rolled a 3, you'd adjust your rolls on the d% table by 15%, increasing your chances of getting the really awesome results that are higher up on the table.
You roll for each of your followers on this d% table, which directs you to one of six sub-tables. Let's talk about each of these:
Table I is the Human Followers subtable. While Clerics can only have 0-level Fighters as followers, and Fighters get 0-level Fighters and one leveled "leader type" of 5-7th level, and Thieves and Assassins get Thieves or Assassins who might be multi-classing if they are demi-humans, a Ranger's human followers might be Clerics, Druids, Fighters, Rangers or Magic-Users. And we're just getting started…
Table II is for demi-human followers. The only demi-human not available as a follower is the Half-Orc.
Table III starts to get interesting. Rangers might have a black or brown bear as a follower, or two giant lynx, or a pair of giant owls… or two blink dogs! Table IV lists possible mounts that follow the Ranger. the options are 1-3 centaurs, a hippogriff or a pegasus! Table V lists creatures, which are all fey or fey-ish: 1-2 brownies, 1-4 pixies, a pseudo-dragon, a satyr or 2-4 sprites.
Finally, Table VI lists "special creatures." The possibilities include 1-2 weretigers, 1-2 werebears, 2-5 treants, a storm giant and… a copper dragon of age category d4+1!
Seriously, Rangers get the best followers - this is the only way I've ever heard of, in any incarnation of D&D, to get a dragon to serve you without having to worry every second about whether it will turn on you or not; granted, the chances are small, but they exist! And consolation prizes include centaurs (that, since they are listed in the "mounts" subtable, will apparently let you ride them), blink dogs, storm giants and pseudo-dragons!
Rangers get the best followers. And if anyone ever mocks AD&D in my presence, pages 16 and 17 of the DMG will be exhibit A as I demonstrate to them just how wrong they are.
While Clerics, Fighters and Thieves mostly get one, two or four short tables for determining followers (and magic-users, illusionists, druids and monks don't seem to get any followers at all), Assassins and Paladins get some commentary that I think is worth commenting on here.
What I find really interesting about the Assassins section is that Gary provides a schedule for the Assassin's followers to show up (which seems to only be for the new followers that a Grandfather/Grandmother of Assassins will attract once they've achieved that title). The first follower(s) (Gary doesn't specify how to determine how many show up as the first to arrive) show up 1d30 days after, "the conditions for obtaining such followers have been met," with the next assassin showing up 1-8 days later, the third one 1-8 days after that and so on. Interestingly, Gary says that if there isn't anyone around to receive the new follower then the follower will wait 1-4 days and then leave forever. I've never seen any kind of schedule like this, but I like it and would consider using it for the followers of all classes.
Moving on to Paladins, who only get a warhorse for for a follower, albeit a very special one, I was surprised to read that, instead of the warhorse just showing up at 4th level, the Paladin instead has a vision of where the warhorse is and must go and get the warhorse, usually having to perform some task, such as taming the warhorse or defeating an enemy of opposite alignment. Gary is kind and stipulates that this, "will not be an impossible task," but should be, "of some small difficulty," that, "will certainly test the mettle of the paladin," and take no longer than two weeks.
A paladin's mount will grow old and need to be replaced every 10 years, which I found surprising, mostly because I just hadn't thought about it before. Gary really does seem to intend AD&D campaigns to last for decades, at least in game time; the aging and death tables weren't for show! Paladin mount hit points are determined not by rolling dice but by halving the Paladin's level and multiplying that by their hit dice (5). I've only seen this kind of hit point calculation done with dragons before. Finally, if the Paladin ever falls, the mount will become an "immutable enemy," apparently not forgiving the Paladin even if he is able to make atonement and redeem himself. And I thought Paladins were uptight…
Also, Rangers get the best followers. Seriously.