From OS X Lion the Users Library folder has been hidden. To find it make Finder the active application, that is when the menu bar displays ‘Finder’ in the top left, select the ‘Go’ menu. Then press the option key (⌥) and select Library.

Standard Finder Go Menu Finder Go Menu

Finder Go Menu with Option (⌥) pressed Finder Go Menu with Option pressed

Option 2, with Finder the active Application press shift-cmd-G (⇧⌘G) for go to folder and type ‘~/Library’