A very handy feature introduced in version 9 of Adobe Illustrator is the ability to assign custom keyboard shortcuts through the Keyboard Shortcuts Menu (alt+shift+ctrl+k or Edit Menu > Keyboard Shortcuts).

In this menu you can assign new shortcuts to the Tools or Menu Commands. When you click on an item a box appears (as shown in the figure above and then you simply enter the key combination by pressing those keys (an example might be something like alt+shift+6). If you happen to use a key combination that is already in use by Illustrator it will warn you and at that point it will give you a choice to Undo, Clear or Go To (this takes you to the conflicting command so that you may modify it)

Using keyboard shortcuts really helps reduce the overall time used in a project and the general annoyance with always having to go to menus with the mouse.