APM is a way to measure objectively your working speed. Someone who can do 20 tasks in one minute is faster than someone who can only accomplish 5.
One way to improve your APM is by using shortcuts. Instead of navigating through menus, try to find the shortcuts from the manual of the software you are using, or look for them on the internet.
I constantly encourage the animators working in one of my projects to use shortcuts for functions they use again and again. If they don’t know them, I say: “GOOGLE IT!”. Like this: "name of function" shortcut in "name of software". Example: Add Frame After Selection shortcut in Toon Boom.
What is better than just using shortcuts? Customizing them! Try to create Keyboard Profiles that have your favorite functions close to one another, Like in video games, in which the most useful functions are in the “QWERTY” area.
If you are serious about improving your APM you should consider buying a Gaming Keypad or Gaming Mouse with extra buttons. I recommend a Gaming Keypad, like Razer Orbweaver or Logitech G13.
One advantage is that you can have keystrokes assigned to one key. For example: Instead of pressing CTRL+SHIFT+R, you only need to press “KEY 1” in your keypad.
Another way is by using macros. Macros are a sequence of keystrokes assigned to a single key. For example: ALT+F, S, (down), Enter - Is a way to reach SAVE A COPY function in After Effects, without navigating through the menus. And it can all be done by just pressing one assigned key on your keypad. That’s a Macro.
What we use is a gaming mouse to which we have assigned macros, the one we prefer is the Logitech G602, but you can get any gaming mouse of your preference.