English Grammar Essentials: 10 Rules That Fix Most Mistakes

Priya Sharma

Priya Sharma writes English learning guides for ESL students. Pune-based language enthusiast.

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Quick answer: Focus on ten rules: third-person -s, subject-verb agreement, a/an/the, word order, questions with do/does, past simple, simple vs continuous, present perfect, countable vs uncountable nouns, and in/on/at for time. Practice one rule per session with five sentences of your own.↗ Share on X

If you have little time to study English grammar, focus on the ten rules that cause most everyday mistakes: the "-s" on verbs after he, she, and it; subject-verb agreement; "a", "an", and "the"; basic word order; questions with "do" and "does"; the past simple; present simple versus present continuous; present perfect; countable and uncountable nouns; and "in", "on", and "at" for time. Learn one rule a day, practice it with five sentences, and ten short sessions will cover the essentials.

Why these 10 rules and not the others?

READ ALSOPick the Right English Tense for Daily Life Easily →How to Remember Irregular Verbs for Everyday Conversation →How to Use “Have” and “Has” in English Questions Correctly →

English grammar books have hundreds of pages. You do not need all of them to speak and write clearly. A small group of rules shows up in almost every sentence you say. When you get those right, people understand you easily and your English sounds more natural.

Here is the plan for the whole article:

Rule 1: When do you add "-s" to a verb?

In the present simple, add -s (or -es) to the verb when the subject is he, she, it, or one person or thing.

• I work. You work. We work. They work.
• He works. She works. My brother works.

Spelling tips:

• Verbs ending in -s, -sh, -ch, -x, -o add -es: watches, goes, fixes.
• Verbs ending in consonant + y change to -ies: study → studies.
• "Have" becomes has: She has a car.

This is the single most common mistake for learners. If you fix only one thing this week, fix this.

Rule 2: How do you make the subject and verb agree?

READ ALSOEasy Rules to Use A and An Without Mistakes →Quick Guide to Pick the Right English Grammar Book for Beginners →When to Use “Since” vs “For” in English Sentences →

A singular subject takes a singular verb. A plural subject takes a plural verb.

• The car is red. The cars are red.
• My friend was late. My friends were late.

Watch out for these tricky cases:

• People is plural: "People are friendly." (not "people is")
• Everyone and everybody are singular: "Everyone is here."
• News is singular: "The news is good."
• A long phrase between subject and verb does not change the rule: "The box of old books is heavy." The subject is "box", not "books".

Rule 3: When do you use "a", "an", and "the"?

These little words are called articles.

• Use a before a consonant sound: a book, a university (it starts with a "y" sound).
• Use an before a vowel sound: an apple, an hour (the "h" is silent).
• Use the when both people know which thing you mean: "Close the door." (there is only one door here)

A simple way to remember: a/an = "one of many, first time mentioned". The = "this specific one".

• "I bought a jacket. The jacket is blue."

No article is needed for general plural or uncountable ideas:

• "Dogs are loyal." (dogs in general)
• "I like music." (music in general)

Rule 4: What is the basic order of an English sentence?

English usually follows this order: Subject + Verb + Object + Place + Time.

1. She (subject)

2. reads (verb)

3. the newspaper (object)

4. in the kitchen (place)

5. every morning (time)

Put adjectives before the noun: "a red car", not "a car red".

Put words like always, usually, often, and never before the main verb but after "be":

• "I always drink coffee."
• "She is always late."

Rule 5: How do you make questions and negatives?

For most verbs in the present, use do or does. For the past, use did. The main verb goes back to its base form.

Common mistakes:

• "Does she likes tea?" → "Does she like tea?"
• "I didn't went." → "I didn't go."

The verb be works differently. Just move it or add "not":

• "Are you tired?" / "I am not tired."

Rule 6: How do you talk about the finished past?

Use the past simple for actions that started and ended in the past, often with a time word like "yesterday", "last week", or "in 2019".

• Regular verbs add -ed: work → worked, play → played.
• Irregular verbs change form. You must memorize them.

Learn these ten common irregular verbs first, because you will use them every day:

Rule 7: "I work" or "I am working"?

• Present simple = habits, routines, and facts. "I work in a bank." "Water boils at 100°C."
• Present continuous (am/is/are + verb-ing) = happening right now or temporary. "I am working from home this week."

Signal words help:

• Simple: always, usually, every day, on Mondays.
• Continuous: now, right now, at the moment, today, this week.

Some verbs are rarely used in the continuous form, such as know, like, want, need, and believe. Say "I know the answer", not "I am knowing the answer".

Rule 8: When do you use the present perfect?

The present perfect is have/has + past participle. Use it when the past connects to now.

• Experience with no exact time: "I have been to Mexico."
• Something that started in the past and continues: "She has lived here for five years." / "...since 2020."
• A recent result: "I have lost my keys." (the keys are still missing)

The key rule: do not use the present perfect with a finished time.

• Wrong: "I have seen him yesterday."
• Right: "I saw him yesterday."

For + a length of time (for two hours). Since + a starting point (since Monday).

Rule 9: "Much" or "many"? "A" or "some"?

Countable nouns can be counted: one apple, two apples. Uncountable nouns cannot: water, money, information, advice, furniture.

Common mistakes:

• "an advice" → "some advice" or "a piece of advice"
• "informations" → "information"
• "How much people?" → "How many people?"

In positive sentences, "a lot of" works with both: "a lot of books", "a lot of time".

Rule 10: "In", "on", or "at" for time?

Think of it as moving from big to small:

• in for long periods: in 2025, in July, in the summer, in the morning.
• on for days and dates: on Friday, on March 3rd, on my birthday.
• at for exact times and short moments: at 7 pm, at noon, at night, at the weekend (British English; Americans say on the weekend).

How can you practice in 15 minutes a day?

Knowing a rule is not the same as using it. This routine turns rules into habits:

1. Minutes 0 to 3: read one rule from this article.

2. Minutes 3 to 8: write five sentences about your own life using that rule.

3. Minutes 8 to 12: say the sentences out loud, twice.

4. Minutes 12 to 15: check your sentences with a grammar checker or a teacher, and write down any mistake.

Keep a "mistake notebook". Every time you make an error, write the wrong sentence and the correct one side by side. Read it once a week. Your personal mistakes are the fastest path to better English.

Your next step

Start with Rule 1 today. Write five sentences about a friend or family member, using he or she, and check that every verb has its "-s": "My sister lives in Chicago. She teaches math..." Tomorrow, move to Rule 2. One rule per session, and after ten sessions you will have practiced all ten essentials.

FAQ

What is the most common English grammar mistake?

Forgetting the -s on verbs after he, she, or it, as in 'He work' instead of 'He works'.

When should I not use the present perfect?

Do not use it with a finished time. Say 'I saw him yesterday', not 'I have seen him yesterday'.

Is 'advice' countable?

No. Say 'some advice' or 'a piece of advice', never 'an advice'.