Apple - How do I create a global keyboard shortcut to create a new note in Notes.app or Reminders.app?

Reminders

You can create a service using the Automator:

1. Open Automator.app
2. Select Service
3. For Reminders: Add action Ask for Text to prompt for a new To Do
4. Add action New Reminders Item
5. Save Service

6. Create Shortcut in:

   System Preferences → Keyboard → Keyboard Shortcuts → Services → Text

Notes

See Mohamad Elwan's answer for notes

For Notes,

Launch Automator --> Service

Add the action "Run AppleScript"

Replace (* Your script goes here *) with:

tell application "Notes" to activate
tell application "System Events"
    click menu item "Notes" of ((process "Notes")'s (menu bar 1)'s ¬
        (menu bar item "Window")'s (menu "Window"))
    click menu item "New Note" of ((process "Notes")'s (menu bar 1)'s ¬
        (menu bar item "File")'s (menu "File"))
end tell

This will work regardless if the Notes app is minimized or hidden.

Then, follow the above procedure to create the global shortcut.

Hope this helps :)