Irregular plurals must be memorized.
Look at this video.
Burke's English
Here is a matching game. Play with a friend. Read and follow the directions.
http://www.manythings.org/wbg/irr_plurals1-mw.html
Here is another game.
http://www.what2learn.com/irregular-plurals-of-nouns/
This will help you build vocabulary.
