Sort of a combination method, I guess you could say. Originally with my setting the idea was to resurrect the ancient nation of Pesh which had been destroyed hundreds of years earlier, and had led to the disappearance or possible destruction of almost all of the elves and dwarves. It also involved finding several relics that had been involved in the same set of events.
So most of the adventures were serial dungeons related to that single campaign idea, though also many of the adventures didn't seem to be about that at first, and the characters were initially unaware of their real objective. That only became more obvious as they recovered things like parts of the Rod of Seven Parts and the Fables of Burdock.
But there were also interspersed throughout the campaign a number of "resting adventures" not related to the main campaign, smaller things only tangentially related to the main quest, if at all. These were small stand alone, get away from it all (rest from the grueling nature of the real campaign, sort of relaxation, diversionary, sometimes comical side-adventures) type walk-abouts. Many of the main campaign adventures involved mega-dungeon, ancient Peshian ruins, buried complexes, that kind of thing.
The "get-aways," though still often dangerous usually involved wilderness adventures, urban adventures, vadding, river and sea trips, mountain climbing, outdoor survival, puzzles or mental games, competitions and duels, etc.
Then again I often adapted and adopted-in some modules (I think many modules back then were particularly good and entertaining, with a little change-up) into the main campaign, or occasionally used them as stand-alone get-away adventures.
Overall though I guess we mostly played one huge, inter-connected campaign, for a long time, until several relics were recovered, some surviving Elven clans were found (who had gone underground into hiding), Pesh was resurrected, several of the main characters were killed and the main Paladin had sacrificed himself in combat to defeat a demon who was trying to prevent Pesh from being revived.
After that the main characters went into hiding or into retirement or became leaders (such as Chief Temple Priest or government leaders) and their children and friends briefly took up where they left off. Then I went off to college and didn't play again for a long time.
Now it's Terra-Ghantik which is kinda hard to classify because you have more than one party with inter-linked interests, and sometimes interlinked adventures and even campaigns.