Nostalrius Begins - Quality wow vanilla realm (1.12)

Hi everyone, i would like to know if all of you complete all quests that you can see or is not necessary do all of them. Cause i try to do the easiest quest, and those necessary when i have nothing to do.

the leveling is based on quest only? or killing monsters its a possible way to level up?

Thanks!

You get experience from completing quests, from killing red/orange/yellow/green mobs and from exploring. Grey quests do give experience as well but only a minimal amount.

Personally I find it far more satisfying to do quests but grinding mobs is a perfectly valid method as well.