What are the most common mistakes in the English language use?

Based on my 10 years as an English teacher, among non-native speakers of English, the most common mistakes:

  • Am/is/as/was/were and "have/has"getting mixed up
  • Overusing "have/has"
  • Overusing simple present tense when other tenses are more appropriate
  • Getting the case wrong on verbs and so missing out the "s" on the end of them
  • Mixing up he/she or his/her
  • Omitting or adding excessive articles "the" and "a"
  • Mispronouncing "th" sounds
  • Mispronouncing "r" sounds
  • Missing punctuation or spaces between words and sentences

Among native speakers:

  • Using "me" in place of "I" or "my". For example, "Where are me glasses?"
  • Putting apostrophes in the wrong place. For example, "Potatoe's only £1/lb" or "How many DVD's do you have".
  • Mixing up less and fewer. For example, most supermarkets have a till signed, "Ten items or less".
  • Mixing up "then/than". Particularly Northern American people as they have become homophonic in North American dialects.
  • Dropping "h" in words that start with "h" like in "hotel", "home" or "hospital"
  • Mixing up i/e in words like "receive", "pier" or "their"
  • Mixing up the letters of "the" when typing fast so as to give "hte" instead. Luckily, modern spell-checkers auto-correct this for us.