If you're familiar with having to find your user data for one reason or another, you may have noticed that the folder seems to be missing in 10.7 or above. In 10.7, Apple chose to hide this folder.
There are a few ways to access this folder now.
Click on the Go menu in the Finder menu bar, press the Option key on your keyboard and select Library.
To navigate to this folder, open the Finder, press Command-Shift-G on your keyboard and enter: ~/Library and press Go.
To change this permanently, you need to use Terminal. (Be careful here because you can cause lots of problems if you do something wrong.) Open the Finder, go to Applications, Utilities, Terminal. Enter the following code exactly as you see it (copy/paste is best) and press Enter.
chflags nohidden ~/Library/
One you have done this, enter the following to restart the Finder:
For more about this, read this blog.
In Mavericks, there is now a Finder Preference setting to re-enable the Library folder.