Preface: As a language learner myself, I find that using mnemonics to remember difficult concepts in a foreign language can help speed up the learning process. This can be accomplished by making up stories for a particular word or grammar structure that can be utterly confusing and impossible to memorize.
I have had a lot of students ask me about how to remember plurals that are the same as their singular counterparts. WELL, my friends, here is a story I thought up that may help you! Note the bold words:
Once upon a time, there was a small forest, high in the beautiful mountains of Chile. In that forest, there were many animals that lived happy, but occasionally violent lives. Many deer and moose would graze peacefully along the crystal-blue lake. Occasionally, they would be interrupted by angry sheep armed with scissors. All of the sheep would try to stab and kill the poor deer and moose. Whenever this happened, the fish in the lake nearby would jump out to their furry friends' rescue. Shrimp and trout of all shapes and sizes would jump into their spacecraft and fly around the sheep, shooting them with lasers. Buffalo riding on watercraft would storm the shore of the lake to help their friends, while swine with assault rifles on hovercraft would zoom in from the surrounding forest to drive out the last of the sheep and their offspring who dared remain behind.
Editor's Note: The more ridiculous the story, the better it will stick in your mind. Please share any fun mnemonic stories you may use for remembering in your target language!