In, Inside, Center
The radical Middle and the kanji Middle are both the same. So if you know one, you know the other.
To remember the reading for this kanji, we use the word Chewbacca to pull up ちゅう in our memory.
If you remember back to the radical 中, the middle of your mouth was stabbed with a stick. You look up to see who did it. There stands Chewbacca, doing his Chewbacca yell. And it isn't a stick in your mouth, it's an arrow from his crossbow (a bowcaster, actually). It just so happens Chewbacca's bowcaster looks just like this kanji too. Go figure.