Experience Points

See here for Experience by Level.

Mob Type Experience Multipliers Note: On some servers, XP can be gained from using spawner mobs and mobs from spawn eggs, however, you should check with the server owner or staff member to make sure. Further, as of version 1.4.04, Wither, Enderdragon, and Witches no longer grant any PVP skills due to their ability to regain health. On some servers, they still grant XP, usually if the mob griefing rule is set to true, to stop the use of these mobs as grinders.

Acrobatics
XP for Acrobatics is calculated by how much damage the player takes after falling from a great height. For example, if you lose 5 hearts you have taken 10 HP fall damage after a jump with no graceful roll, then that damage will be applied to the formula below in a gain of 0.001

XP. You will also get XP on successful dodge maneuvers in combat..