Putting your applications folder in your dock enables you to get rid of icons in your dock that you rarely use, and still have 1-click access to all of your installed applications. This not only keeps your dock clutter-free, it makes it easier to navigate to your applications folder after you install an application. (For example, a recent freeware install.)
1. Open a new Finder window.
2. Click on “Macintosh HD” (or your hard drive if you've renamed it)
3. Drag your Applications folder to the dock and release.
Important: You can't drag it from the sidebar of the finder widow.
Important: You can't place the Applications folder in the main portion of the dock. It must be placed next to the “Trash”