How is experience gain determined when killing minions and/or other champions? Does last hitting change experience? Distance from minions? Is experience for champion kills handled the same way?
From the LoL Forums
For minions on Summoner's Rift:
Time starts from game start, not from the initial minion spawn. Minions increase in exp if they spawn after the "x" minute mark.
Last hitting doesn't change the experience gained. Neither does distance - you either get the experience or you're too far away. That's why zoning is so effective.
From LoL Wiki:
EDIT: Additionally, you have to factor in +exp masteries and runes, if you have either of them or both.
In addition, when more than 1 champion is sharing experience, 10% extra experience is split among all champions.
To add to the above poster's information: don't forget that Zilean's passive, Heightened Learning, will also increase your team's experience gain by 8%.