just tossing it out there, that i got Gavaine nearly to level 10 now in the 4-3 months i have been playing him, hitting "the grind" (dungeoning, killing things on my way to and from places) around six times, and never for very long.
Someone told me once that the more people you rp with, the greater the rp bonus. Also you get xp from quests/jobs and being involved in DM moments. Alone, no, you don't. But that didn't stop me from rping with myself and only myself when i was locked up someplace. I am fairly certain i got some XP for that that i didn't notice, because my next rest gave me a level.
Best way to level is not to think about it. Let me say it again. The BEST way to level, Is NOT to think about it.