Leveling in an MMO is always a challenge. Often, it's more of a challenge just to stay awake than it is to actually succeed, but more often than not I find myself poking around to see if there's any cool ways to level. In EverQuest, grinding was all there was. Quests weren't really a way to level and instanced dungeons didn't really exist (they were added late in that game's evolution).
In WoW, your options were: dungeons or quests. If you had some friends with lots of spare time to help you, there was also a grinding method that worked well, but it required a tolerance for boredom that was nearly superhuman. Later on, PvP also became a lesser, but viable option.
In classic Rift, the options exploded. You had rifts, quests, PvP, dungeons, zone events and the usual grinding strategies. Then Storm Legion landed.