When it comes to delving into history – any history, not just the history of RPGs – I tend to favor documents over memories, especially my own memories. Memories, after all, are tricky things, especially the memories of middle aged and older people. More times than I care to admit, I was sure I remembered something that was later proven, through documentary evidence, to be untrue or at least misconstrued. Documents don't tell the whole story, of course; divorced from context, they can be just as prone to being misconstrued as memories (and that's not even taking into account deliberately false documents). Nevertheless, I tend to think we're on more solid ground in examining history when we have physical evidence, which is why I have such respect for the work of people like Jon Peterson, whose careful examination of early RPG documents have revealed a great deal about the history of the hobby.
To that end, one of current activities is re-reading many of the RPG periodicals, both professional and amateur, I still have from the '70s and '80s. Though TSR's Dragon is quite useful in this regard, I'm finding that the Polyhedron is sometimes much more intriguing. Whereas the articles in Dragon tended to be both more polished and "theoretical," those in Polyhedron were (generally) rougher and more focused on "practical" considerations. In the process of re-reading those issues of Polyhedron I still have, I've come across a number of articles that seem to have arisen out of a referee's attempts to deal with some problem or other in his campaign.
A good example of what I'm talking about is Brian Leikam's "In Defense of the Lowly Fighter," which appears in issue #30 of Polyhedron (July 1986). Leikam was a RPGA tournament winner, as well as a member of the US Air Force, who ran a Dungeons & Dragons campaign at Whiteman Air Force Base in Missouri (or so says his author bio). It's also noted that he was "pleased with the convenience and playability" of the D&D (as opposed to AD&D) system. The article attempts to grapple with the fact that "no one seems to play fighters anymore" and that D&D campaigns are "overrun with 'rare' demihumans and spellcasters." To that end, Leikam proposes some solutions that have worked for him in his own D&D campaign.
I genuinely enjoy articles of this sort, both for what they tell us about the perception of supposed "problems" in the rules of Dungeons & Dragons and how individual referees dealt with them in their own campaigns. This is the kind of documentary evidence of which I want to see more, if only because it provides a useful counterpoint to the frequent cries of "I never saw that back in the day" or "We did it this way." Again, I don't want to discount memories entirely, but, speaking for myself, my own memories are so often hazy (or rose colored) that I think it's vital to buttress one's memories with additional testimony.
Leikam's assertion that fighters were often rare is, I think, right. That's certainly my recollection, particularly in AD&D, where rangers and paladins were much more commonplace, despite the supposed ability score restrictions. His comments about the prevalence of demihumans likewise comport with my experiences, though I mostly played AD&D rather than D&D. Regardless, Leikam proposes three solutions, only two of which interest me at the moment. Here's one of them:

This solution, as such, doesn't concern me so much as his claim that D&D and AD&D "are generally not compatible." I'm somewhat baffled by this statement. What does he mean by "not compatible?" In the context of demihumans, there might be some truth to it, inasmuch as D&D uses race-as-class and AD&D does not. On the other hand, nearly despite Gygax's regular assertions that the two games were completely different and never, ever, ever to be mixed, they not only were mixed but done so often by nearly everyone who played the games during this era – or so my memories tell me. It's a very peculiar thing to say and wonder what he meant by it.
The other suggestion that interests me is the following one:

This solution mentions that "demi-humans are supposed to be the minority in most worlds." I firmly agree that D&D (and AD&D) imply and sometimes outright state that this is supposed to be the case, but my memories tell me that very few people ever adhered to it. I certainly would have preferred it to be the case, but I think demihumans – dwarves and elves in particular – were simply too popular among players to make this work. In my recent OD&D campaigns, I set a strict limit of no more than a single instance of a demihuman race among the player characters, such that the PC elf was the elf in the campaign rather than being one of several. Most NPCs had never seen an elf before and, to hit that home, I was extremely stingy on including demihuman NPCs as well. Unlike Leikam, my concern had little to do with rules and more to do with tone: I prefer that most characters are human, in keeping with the pulp fantasy sensibilities I prefer.
I am deeply interested in how people actually played Dungeons & Dragons and other RPGs in the first decade of the hobby's existence, in particular the kinds of fantasy inspirations they drew upon and how those influences shaped the shared worlds they created. Equally interesting is the interplay between the "official" intent of TSR and the desires of those who picked up the game and made it their own. That's why I'm seeking out as many documents of that era as I can find. They not only make for some excellent reading, they shed light on these and related questions.