There isn’t a definitive list of exactly 12 grammar rules that can encompass all aspects of English grammar comprehensively. However, there are several fundamental rules that everyone learning English should be familiar with:

1. Subject-Verb Agreement: Ensure the subject of a sentence agrees with the verb in terms of number (singular/plural).
2. Sentence Structure: Clear sentences should have a subject, verb, and often an object, such as “Subject-Verb-Object.”
3. Tense Usage: Understanding how to correctly use present, past, and future tenses in sentences.
4. Punctuation: Knowing how to properly use punctuation marks like periods, commas, question marks, exclamation points, etc.
5. Word Order: Adhering to the proper order of words in a sentence to convey meaning clearly.
6. Parts of Speech: Knowing the different parts of speech such as nouns, verbs, adjectives, adverbs, etc., and how they function in sentences.
7. Capitalization: Understanding when to capitalize words like proper nouns, the first word in a sentence, etc.
8. Pronoun Usage: Correctly using pronouns to replace nouns and maintain clarity.
9. Agreement in Gender and Number: Ensuring consistency in gender and number when using pronouns and determiners.

10. Articles: Knowing when to use “a,” “an,” and “the” correctly.

11. Parallel Structure: Maintaining parallel structure in lists and comparisons for coherence.

12. Double Neg