If you are a regular user of Photoshop, you will find it rather time consuming to select each tool from the tool bar manually. To save time, you can use the shortcut keys which can speed up the process of selecting the tools.

Below is a link for Photoshop keyboard shortcuts for both windows and mac:
http://help.adobe.com/en_US/Photoshop/11.0/WS24E993BC-E1F3-4ac6-8225-7685C3B17669a.html

You can also customise your own Photoshop keyboard shortcut. This avoids you having to use the default shortcuts. To customise the shortcuts you can either select:

• Edit > Keyboard Shortcuts (Windows)
• Windows > Workspace > Keyboard Shortcuts (Mac)

To find more information on keyboard shortcuts checkout:
http://help.adobe.com/en_US/Photoshop/11.0/WSfd1234e1c4b69f30ea53e41001031ab64-76b7a.html