When in a battleground, what things will grant experience? At my current low level, killing a player doesn't seem to give anything. Capping a flag in WSG or a base in AB will. Anyone know of anything else? All in all, it seems to be really slow, like 10% of a level in a 20 min BG. Will this improve when I get to higher level?
I'm afraid that the only way to accumulate experience points through PVP is to accomplish objectives in Battlegrounds (honourable kills are not included). To answer your second question the XP you gain will likely increase in proportion with your level however it is also likely that the time in PVP needed to advance another level will increase as per the Higher level = Increased time questing to advance to the next level.
Hope this helps