Rename - because giving things meaningful names is the best way to write self-documenting code. Shift+Alt+R
Extract method - whenever a method gets too long. Shift+Alt+M
Extract constant - because magic numbers are bad. Shift+Alt+T (refactoring menu, there's no direct shortcut).
Inline/introduce variable - to remove clutter from methods. Shift+Alt+I (inline), Shift+Alt+L (introduce)
