Is there that one menu command you always use in After Effects and wish there was a keyboard shortcut? In the past, there were cumbersome methods of modifying a text file buried in the filesystem to change things. But there's a much easier way:

System Preferences: Keyboard & Mouse.

Go to the Keyboard Shortcuts tab and click on the "+" button towards the bottom.

Then select After Effects from the Application pulldown (you might have to go to "Other…" at the bottom and browse to AE).

Type in the exact name of the menu item you want a shortcut for, then hit the keys you'd like to be the shortcut. Just make sure they shortcut isn't already used by After Effects.

And there you go!