How useful are mnemonics?

 A mnemonic is a memory aid — a hook, a technique, phrase, pattern, image, or acronym that helps you remember information more easily. Language teachers usually think of them as acronyms. Ones I learned at school were DOGWUF in German (to remember prepositions which take the accusative case) and MRS DAVENTRAMP (for remembering French verbs which use être as their auxiliary in the perfect gense).

Here are some others you may know or like. Many of these were shared by teachers on Facebook when I was drafting our book about memory (Memory: What Every Language Teacher Should Know (Smith and Conti, 2021)).

French

French mnemonics	What they refer to
EN for engine	Using en in repositional phrases for motorised means of transport, e.g. en voiture versus à pied
A TV AND MRS PERM MR DRAPERS MT VAN MR VAM RRED PANTS DR PV MASTERMAN DR VEMS MANTRAP MR DREAMPANTS	The verbs which take the auxiliary être in the perfect tense (allowing for slight variations of verbs included)
WEDDINGS	Uses of the subjunctive: Will, Emotions, Doubt, Desire, Interrogation, Negation, General characteristics, Superlative
BANGS BRAGS (R = rank)	Adjectives which precede the noun: Beauty, Age, Number (ordinal), Greatness, Size
CRFL (careful)	Consonants which are most commonly pronounced at the end of words
CROISSANT	Elements to include in a piece of intermediate writing; Connectives, Reasons, Opinions, Infinitive expressions, Subject pronouns ( a range thereof), Star phrases, Adjectives and adverbs, Negatives, Tenses (a range thereof)
AVOCADO	Similar to above, but: Adjectives, Verbs, Opinions, Connectives, Adverbs, Description, Originality
STuPiD DPSTXZ (dipsticks)	Consonants which are usually not pronounced at the end of words
“A” and “le” will never do, what do you do, you put A-U!	To remind students not write “à le” instead of “au”
♬ me te nous vous, me te nous vous le la les, le la les lui leur, lui, leur y en, y en (to the tune of Frère Jacques)	Order of pronouns
A donkey says y en	Order of pronouns

German

German mnemonics	What they refer to
FUDGEBOW BE DOG WUF	Prepositions which take the accusative case
BRATWURST	Elements to include in a piece of intermediate writing: Belief (opinion), Reason, Adjectives and adverbs, Tenses, Word order, Umlauts, Range, Structures, Time phrases
RAINCOAT	Similar to above, but Reasons, Adjectives, Intensifiers, Nouns (need capitals), Connective, Opinions, Adverbs (of time, manner, place) and Tenses
Elephants STir Tetley ENglish Tea ENergetically	Present tense regular verb endings
VBZGASMAN (Very Busy Gasman)	Prepositions which take the dative case
WEIL is so vile, the verb runs a mile!	Verbs goes to the end of the clause or sentence
WOW DAD	Subordinating conjunctions: weil, obwohl, wenn, da, als, dass
Tickle Me Pink	Order of adverbs: Time, Manner, Place
I AM a DR	Prepositions which take the accusative involve movement (Accusative Movement), while those which take the dative indicate rest (Dative Rest)

Spanish

Spanish mnemonics	What they refer to
DOCTOR PLACE	When the verbs ser an estar are used Ser: Date, Occupation, Characteristic, Time, Origin, Relation Estar: Position, Location, Action, Condition, Emotion
CAROLINA	Letters in Spanish which can be doubled, e.g. the “r” in carro or “l” in llave
UWEIRDO	Use of the subjunctive: Uncertainty, Wishes, Emotions, Impersonal expressions, Recommendations and requests, Doubt and denial, Ojalá
Vin Diesel has ten weapons	Irregular imperatives: sé, ven, di, sal, haz, ten, ve, pon
My Big Dog Poops Under Trees	Qualifiers : muy, bastante, demasiado, poco, un poco, tan
DISHES	Irregular subjunctives : dar, ir, ser, haber, estar, saber

How useful are mnemonics for developing language proficiency? 

Short answer: not very. But they can help students monitor the accuracy of their speech and writing, remember rules of phonics or remind them of elements to include in written assignments. They contribute to students' knowledge of grammar and are fun to use. We might mentally refer to them when speaking too. I would say say that help with what Krashen calls learning, rather than acquisition. Namely, the declarative knowlege we hold about the new language but which only very indirectly, if at all, contributes to our ability to comprehend and use language in real time.

So my message would be: have fun with mnemonics, but be realistic about how useful they are. Keep the focus on providing comprehensible input and communication, using whichever approach fits your context best.