Opening up another copy of an application that is already open with the new taskbar can be tricky. Normally when you click on a taskbar item it just switches to the open windows. The trick to opening a new copy of the application that is already open is to hold down Shift while you click on the icon.
To launch an application as Administrator hold down CTRL and Shift when you click on the icon.
Another useful keyboard trick will help you launch taskbar items without clicking. Instead of clicking on the first taskbar item just hold down the Windows key press number 1. For the second taskbar icon, Windows key + 2 and so on.
To switch through open taskbar items and view the thumbnails use the Windows key + T