Well, I'm from Ragnarok, so I can't help with the first thing, but for the second, people head over to Gusgen Mines to do what is called "Fields of Valor" on Skeleton monsters, starting at 10-15 til they reach 30, then head over to the Crawler's Nest til 60, and then Bostaunieux Oubliette til I have no clue...
Or they leech off people in Abyssea (which is usually frowned upon by the serious players)... >w>()
Leveling is super easy now-a-days.
Most people worry about getting the best armor, fighting end bosses, doing quests, getting to level 99, maxing out skills and merits, that kind of thing.