Common Mistakes in English

1. Usage of "marriage anniversary" in place of "wedding anniversary"
2. Usage of "doubt" in place of "question"
3. Usage of "have/had had"
4. Confusion between usage of "there", "their" and "they're"
5. Confusion between usage of "loose" and "lose"
6. Usage of "cope up with" instead of "cope with"
7. Usage of "my/your/our-self/selves" after resist.
8. Usage of "take out" instead of "find/calculate"
9. Usage of "How is [x] like?" instead of "What is [x] like?"
10. Usage of "Many a times" instead of "many times/many a time/a lot of times"
11. Usage of 'You need not to [do x]' instead of 'you need not [do x]' or 'you do not need to [do x]'
12. Usage of "return back", "revert back", "reply back", etc. instead of "return" "revert", "reply", etc.
13. Usage of "competition" after debate or quiz.
14. Usage of plurals after "doesn't" such as 'doesn't fits', 'doesn't matters' instead of 'doesn't fit', 'doesn't matter'
15. Addition of "about" like in 'Discussing about [x]' instead of 'discussing [x]'
16. "Commonsensical" instead of "matter of common sense". Commonsensical is not a word.
17. "Be rest assured" instead of "rest assured" or "be assured".
18. Usage of additional "as" after "called" like in "This website is called as Quora"
19. Usage of "but" along with "although"
20. Usage of "if yes/not" instead of "if your answer is yes/no"
21. Usage of "know more" instead of "find out more"
22. Usage of standalone "basis" instead of "on the basis of" in a sentence.
23. Usage of "equally as [adjective] as" instead of "as [adjective] as"
24. Usage of "did" instead of "made" as in "I did a mistake"
25. Usage of "me" right after "suggest/recommend"
26. Usage of "off" instead of "of"
27. Usage of a negative condition with "until/till"
28. Using 'Myself [so-and-so]' in place of 'I'm [so-and-so]'.
29. Usage of "I don't think so that.." instead of "I don't think that.."
30. Usage of [verb in the past tense] after "didn't"
31. Usage of 'More [comparative adjective that ends in -er]' instead of only [comparative adjective that ends in -er]
32. Usage of plural form instead of singular form like alumni instead of alumnus.
33. Usage of "was" with "if/wish"
34. Usage of "Who" with a relative pronoun
35. Usage of between instead of among.
36. When using or, either, neither, nor the succeeding verb would follow the form nearest to it.
37. Usage of two comparative terms together.
38. Usage of suffixes with Roman numerals.
39. Usage of "pass out/away" instead of "graduate". [Not always - Google]
40. Usage of "see/look at/watch"
41. Usage of goggles/shades/glasses-spectacles. (Correct: "... a pair of goggles...")
42. Usage of "on the" instead of "on a".
43. Usage of 'only' to emphasize actions.
44. More better instead of "better" or even "better".

45. Usage of has/have; for example 'I has/You has' instead of I have/ You have'

Source :https://www.quora.com/Grammar/What-are-the-most-common-English-language-and-grammatical-errors-made-by-people-from-India