Take a look at the action that is currently assigned to the shortcut you wish to use for something else. If it's something you don't use and don't see yourself interested in using with said shortcut... delete away.
If it makes you say "Hold on... That's really intuitive for that other action and I might even use that! Let me pick a different shortcut here."
Then there you go.
Here's a tip:
When you pick a keyboard shortcut for some action...
You thought up the perfect intuitive shortcut that you'll never forget.
Now put it in one of the menus too!
The menus display the assigned keyboard shortcuts. (A stock feature of the OS.)
So when you've forgotten that perfect shortcut the next day, you can click on a menu and refresh your memory quickly. (Cause you'll probably also have forgotten the name of the action and have a pissy time searching for it in the action list.)