Selecting targets

Alt-click, press E on what you are looking at, or Q for yourself.

KeysAlt + Left MouseEQ
Alt + Left Mouse
Select the player, creature, corpse or building under the cursor.
E
Select whatever is under the crosshair (over-the-shoulder camera).
Q
Select yourself.

Your target appears in the frame at the top of the screen with its name, level and health.

Aimed powers and shots go to what is under the crosshair first, and to your selected target otherwise. Many things, such as trading, a building's window or a horse's figurine, act on your selection.