I started in August, '75. My friend and I had been playing wargames for a year or two before OD&D, and my friend had a sand table in his garage for miniatures battles using Chainmail rules, so the transition to OD&D seemed like a smooth one. At first it was just the two of us, where one would run and the other play and then we would switch roles. Eventually we added a third DM so that we could have games all weekend, and then more players started to add in as they heard us talking about the game at school. Back then, everyone in our group read Conan, Fafhrd & Grey Mouser, and Elric so most of our campaign ideas followed plotlines similar to the style from those sources. A couple of us were into Barsoom, so I ran a lot of do-gooder characters and my buddy's campaign often followed a "save the princess" theme for me. Back then, folks just said what kind stories they liked and we made up scenarios to do those styles, rather than buying campaigns which might or might not interest any individual player.
We spent a lot of time early on just exploring deeper and deeper dungeons, then created a town so that characters could buy stuff in between adventures, then a small region of wilderness so that characters could travel to and from the dungeon. It all grew up in a slow and piecemeal manner where we would realize we needed something (a castle, a city, a dungeon) and just design it on the spot. As we built our campaign worlds to take up more and more area, we added in more kingdoms and fought occasional battles between baronies using Chainmail rules. Often we would run more than one character at a time, perhaps one "baron" and one "adventurer" so that we could play politics and spies at the same time. What was interesting was that those characters weren't always on the same side, so your baron would be trying to accomplish something while your adventurer was trying to stop it. Most of the time, however, there was an evil king or an evil wizard trying to rule the world so all of us would band together to try to defeat the bad guys.
I was a charter subscriber to the Judges Guild subscription so I got the CSIO, Thunderhold, and other "modules" which made appearances in my campaign. The CSIO was interesting because it had cool stuff you could stumble upon without me having to plan it in advance. The CSIO was used in almost every campaign I ran in the 1970's and 1980's, only sometimes it was called Greyhawk, sometimes Lankhmar, or Aquilonia, or whatever city was needed at the time. I stole a lot of place-names from literature (still do, actually) to help my prep because I would already have a clue what might be found there. Back in those days everyone that I knew made their own campaign maps and nobody played in a store-bought campaign, with the exception of the JG materials that I used in my game.
For me, the "early days" were all about fun and flexibility. We didn't get really hung up in rules debates (not until AD&D came out, that is, when our "rules lawyers" began to take over) and we rewarded player creativity. Some of our players didn't know the rules very well, had never read the rulebook, and had no interest in reading the rulebook; they just played and enjoyed the action. I won't say that it was a "role versus roll" thing because we didn't think in those terms back then, but characters with similar stats might seem very different because of the way they were played. A fighting man who was a noble might play very different from a fighting man who was a sergeant. We sort of got "into" persona and that guided us a lot more than the game bonuses. Sometimes we would set up a "family tree" and play through a character, son of a character, grand-son of a character, and so on.
I won't say that this style of play was "better" then what I see at game stores now, but it was different.