It's been asked many times, but depending on the current state of the game, the answer changes occasionally. As the game stands now, your best bet to just level is, in order:
1. Get/find/pay a higher level character to power-level you.
2. Play during high population periods, and queue for every SC you can while spending the rest of your time in the RvR lakes in a WB (or solo with AAO if you are a DPS class.)
3. Play during off-peak, take whatever SC pops you can get, and grind the rest.
Questing, as it stands now, is fairly useless for leveling (with only a few exceptions), so your best bet is to play during EU peak time, or grind during NA.
4. Using siege equipment solo (oil, cannons, etc), especially with AAO, is an exception to the above, and if you are in the right place at the right time can yield ridiculous gains in both experience and RR. Not very sporting, but it is possible, and therefore used/abused quite often.
Good luck, and see you in game
