To modify keyboard shortcuts, use the KeyEd Up script from Jeff Almasol, which is available on the Adobe After Effects Exchange website.
Sebastien Perier provides instructions on his website for assigning keyboard shortcuts to scripts so that you can run a script with a single keystroke. This technique relies on the KeyEd Up script.
For information on remapping keyboard shortcuts for keyboard layouts other than the standard US English layout, see Jonas Hummelstrand’s website.
For a reference of keyboard shortcuts, see Keyboard shortcuts reference.