Grammar mistakes can sneak into anyone's writing or speech, even if you've been learning English for years. The good news? Most errors follow predictable patterns, and once you understand the rules behind them, avoiding mistakes becomes second nature. This guide walks you through 29 grammar tips that address the most common slip-ups English learners make. You'll get straightforward explanations, real-world examples, and memory tricks to help everything stick.

1. Subject-Verb Agreement

Your subject and verb need to match in number. If the subject is singular, use a singular verb. If it's plural, use a plural verb.

Examples:

  • She walks to school every morning.
  • The students walk to school together.
  • The book on the shelf belongs to me.

Memory trick: Strip away all the extra words between the subject and verb. "The book... belongs" makes it easier to see they match.

2. Its vs. It's

"Its" shows possession (belonging to it). "It's" is short for "it is" or "it has."

Examples:

  • The dog wagged its tail.
  • It's raining outside.
  • It's been three years since we met.

Memory trick: If you can replace the word with "it is" or "it has," use the apostrophe.

3. Your vs. You're

"Your" shows possession. "You're" means "you are."

Examples:

  • Is this your jacket?
  • You're going to love this movie.
  • Your presentation was excellent.

Memory trick: Same as above—try replacing it with "you are." If that works, you need the apostrophe.

4. There, Their, and They're

"There" refers to a place. "Their" shows possession. "They're" means "they are."

Examples:

  • Put the box over there by the window.
  • The neighbors left their car unlocked.
  • They're coming to dinner at seven.

Memory trick: "There" has "here" hiding inside it (both about place). "Their" has "heir" in it (someone who inherits things—possession). "They're" = they are.

5. Affect vs. Effect

"Affect" is usually a verb meaning to influence. "Effect" is usually a noun meaning the result.

Examples:

  • Lack of sleep can affect your concentration.
  • The medicine had an immediate effect.
  • His words didn't affect me at all.

Memory trick: Affect is an Action. Effect is the End result.

6. Then vs. Than

"Then" relates to time. "Than" is used for comparisons.

Examples:

  • We had lunch, then went shopping.
  • She's taller than her brother.
  • Back then, things were different.

Memory trick: "Than" is for comparisons (both have an "a").

7. Fewer vs. Less

Use "fewer" for things you can count. Use "less" for things you can't count.

Examples:

  • There are fewer students in class today.
  • I have less time than I thought.
  • We need fewer chairs and less noise.

Memory trick: If you can count it with numbers (one, two, three...), use "fewer."

8. Who vs. Whom

"Who" is the subject doing the action. "Whom" is the object receiving the action.

Examples:

  • Who called you last night?
  • To whom did you give the letter?
  • She's the person who helped me.

Memory trick: Replace with "he" or "him." If "him" works, use "whom." If "he" works, use "who."

9. Me vs. I

Use "I" when you're the subject. Use "me" when you're the object.

Examples:

  • Sarah and I went to the concert.
  • The teacher gave Sarah and me extra homework.
  • Between you and me, I think he's wrong.

Memory trick: Remove the other person from the sentence. You wouldn't say "Me went to the concert," so "Sarah and I" is correct.

10. Could Of vs. Could Have

"Could have" is correct. "Could of" is always wrong—it just sounds like "could've" when spoken quickly.

Examples:

  • I could have finished earlier. ✓
  • She should have called. ✓
  • They might have forgotten. ✓

Memory trick: "Of" is not a helping verb. You can't "of" done something.

11. Apostrophes for Possession

Add 's to show possession for singular nouns. For plural nouns ending in s, just add an apostrophe.

Examples:

  • The teacher's desk is cluttered.
  • The teachers' lounge is on the second floor.
  • James's book or James' book (both acceptable).

Memory trick: One owner = 's. Multiple owners ending in s = just '.

12. Apostrophes Don't Make Plurals

Never use an apostrophe to make something plural (except in rare cases like "mind your p's and q's").

Examples:

  • I bought three books. ✓ (not book's)
  • The 1990s were amazing. ✓ (not 1990's)
  • Two coffees, please. ✓

Memory trick: Apostrophes show ownership or contraction, not "more than one."

13. Double Negatives

Two negatives make a positive in English. Avoid using two negative words together.

Examples:

  • I don't have any money. ✓ (not "I don't have no money")
  • She hasn't seen anyone. ✓ (not "She hasn't seen nobody")
  • There isn't anything left. ✓

Memory trick: One negative per sentence keeps your meaning clear.

14. That vs. Which

Use "that" for essential information (no comma). Use "which" for extra information (with a comma).

Examples:

  • The book that I borrowed is overdue. (which specific book? Essential info)
  • My favorite book, which I've read twice, is on my shelf. (extra detail)
  • Cars that run on electricity are becoming popular.

Memory trick: If you can remove the clause and the sentence still makes sense, use "which" with commas.

15. Who vs. That (for People)

Use "who" when referring to people. "That" can refer to things or sometimes people, but "who" sounds more natural for people.

Examples:

  • The woman who lives next door is a doctor.
  • The students who passed the test celebrated.
  • The car that broke down was really old.

Memory trick: People deserve "who"—it's more respectful and specific.

16. Dangling Modifiers

Make sure the describing phrase clearly connects to what it's describing.

Examples:

  • Wrong: Walking to school, the rain started pouring. (the rain wasn't walking)
  • Right: Walking to school, I got caught in the rain.
  • Wrong: After studying all night, the test was easy.
  • Right: After studying all night, I found the test easy.

Memory trick: Ask yourself "who's doing this action?" right after the comma.

17. Run-On Sentences

Don't stick two complete sentences together with just a comma. Use a period, semicolon, or conjunction.

Examples:

  • Wrong: I love pizza, it's my favorite food.
  • Right: I love pizza. It's my favorite food.
  • Right: I love pizza; it's my favorite food.
  • Right: I love pizza, and it's my favorite food.

Memory trick: If both parts can stand alone as sentences, they need more than a comma to connect them.

18. Sentence Fragments

Every sentence needs a subject and a verb to be complete.

Examples:

  • Fragment: Because I was tired. (incomplete thought)
  • Complete: I went to bed early because I was tired.
  • Fragment: Running through the park.
  • Complete: She was running through the park.

Memory trick: Read it out loud. Does it feel finished, or does it leave you hanging?

19. Lay vs. Lie

"Lay" means to put something down (it needs an object). "Lie" means to recline (no object needed).

Examples:

  • Please lay the books on the table. (laying what? Books)
  • I need to lie down for a bit. (just me, no object)
  • She laid the baby in the crib. (past tense of lay)
  • He lay on the couch yesterday. (past tense of lie)

Memory trick: You lay something down. You lie down yourself. Past tense gets tricky: laid/lay/lain—just practice these separately.

20. Good vs. Well

"Good" is an adjective (describes nouns). "Well" is an adverb (describes verbs).

Examples:

  • That's a good movie.
  • She sings well.
  • I feel good today. (describing your emotional state)
  • I'm doing well. (describing how you're functioning)

Memory trick: You do things well, but things are good.

21. Loose vs. Lose

"Loose" means not tight. "Lose" means to misplace or not win.

Examples:

  • These pants are too loose.
  • Don't lose your keys.
  • The team might lose the game.

Memory trick: "Lose" lost an "o"—just like you lose things.

22. Accept vs. Except

"Accept" means to receive or agree. "Except" means excluding or but.

Examples:

  • I accept your apology.
  • Everyone went except Tom.
  • She accepted the job offer.

Memory trick: Except means excluding.

23. Complement vs. Compliment

"Complement" means to complete or go well with. "Compliment" means to praise.

Examples:

  • That wine complements the meal perfectly.
  • He gave me a nice compliment about my work.
  • The colors complement each other.

Memory trick: "I like to give compliments" (both have "i").

24. Principle vs. Principal

"Principle" is a fundamental rule or belief. "Principal" is a person (like a school principal) or means main/primary.

Examples:

  • She has strong moral principles.
  • The principal called a meeting.
  • The principal reason I left was the long commute.

Memory trick: The principal is your pal. Principle is a rule.

25. Stationary vs. Stationery

"Stationary" means not moving. "Stationery" is writing paper.

Examples:

  • The car remained stationary at the red light.
  • I bought new stationery for my letters.
  • The bike is stationary on its stand.

Memory trick: Stationery contains "e" like "envelope."

26. Ensure vs. Insure vs. Assure

"Ensure" means to make certain. "Insure" relates to insurance. "Assure" means to reassure someone.

Examples:

  • Please ensure all windows are locked.
  • I need to insure my new car.
  • I assure you everything will be fine.

Memory trick: Ensure makes things sure. Insure protects with insurance. Assure calms a person.

27. Between vs. Among

Use "between" for two things. Use "among" for three or more.

Examples:

  • Choose between the red shirt and the blue one.
  • The secret spread among all the students.
  • Between you and me, I'm nervous.

Memory trick: "Between" and "two" both have "tw" sounds (kind of).

28. Farther vs. Further

"Farther" refers to physical distance. "Further" refers to metaphorical or additional things.

Examples:

  • My house is farther from school than yours.
  • We need to discuss this further.
  • He walked farther than anyone else.

Memory trick: Farther has "far" in it—physical distance.

29. Each Other vs. One Another

Traditionally, "each other" is for two people/things, and "one another" is for three or more. Most people use them interchangeably now, but knowing the traditional rule helps in formal writing.

Examples:

  • The two friends help each other.
  • All the team members support one another.
  • The couple looked at each other.

Memory trick: Keep the traditional rule for formal essays, but don't stress about it in everyday conversation.

Practice Section

Try filling in the blanks with the correct word:

  1. The dog wagged _ tail happily. (its/it's)
  2. She's much taller _ I expected. (then/than)
  3. _ going to the party tonight? (Your/You're)
  4. The weather can _ your mood. (affect/effect)
  5. There are _ people here today. (fewer/less)
  6. I should _ studied harder. (of/have)
  7. The woman _ lives next door is friendly. (who/which)
  8. Please _ the papers on my desk. (lay/lie)

Answers: 1. its, 2. than, 3. You're, 4. affect, 5. fewer, 6. have, 7. who, 8. lay

Wrapping Up

Grammar mistakes happen to everyone, but now you've got 29 solid tips to help you catch the most common ones. The trick isn't memorizing every rule perfectly—it's building awareness so you naturally pause and think when you're writing or speaking. Start by picking two or three tips that address mistakes you make most often, and focus on those first. Once they become automatic, move on to the next ones.

Keep practicing in real situations. Write emails, send messages, join English conversations. Each time you use these tips correctly, they'll stick a little better. Most people miss this part: grammar isn't about perfection, it's about clear communication. The clearer you communicate, the more confident you'll feel in English.

So take what works for you from this list, and start using it today. You've got this.