Common errors

Although editing ranges from simply correcting typographical errors to re-writing substantial portions of text, much of it comprises correcting straightforward errors in

•  spelling
•  punctuation
•  grammar.

Spelling

The following words (British English) are often misspelled:

absorb, absorption, accessible, accommodate, aggravate, auxiliary, barbecue, calendar, cemetery, collectible, dependent, desperate, disparate, ecstasy, eczema, eighth, exhilarate, fluorescent, fulfil, hæmorrhage, harass, heroes, indispensable, inoculate, intercede, lens, liaison, licence, license, lieutenant, likelihood, likely, manageable, manœuvre, millennium, mosquitoes, occasion, occurred, occurrence, panicky, parallel, parliament, perseverance, persistence, picnicking, possess, potatoes, precede, preference, proceed, procedure, pronunciation, pursue, questionnaire, recede, recurred, renege, rhythm, satellite, secede, separate, skiing, subtle, supersede, susceptible, symmetrical, truly, twelfth, withhold, yacht.

Punctuation

In the following pairs, the first one is incorrect.

✖  The man wearing a grey coat and carrying a thin cane, stepped off the bus. (incorrect)
✔  The man wearing a grey coat and carrying a thin cane stepped off the bus. (correct)

✖  The man has lived in Wellington, New Zealand all his life.
✔  The man has lived in Wellington, New Zealand, all his life.

✖  After a long holiday in the south of France he returned to work.
✔  After a long holiday in the south of France, he returned to work.

✖  Barrys Bus's
✔  Barry's Buses

✖  John worked hard and passed his exams, he was only 20 when he completed his degree.
✔  John worked hard and passed his exams. He was only 20 when he completed his degree.

✖  He took with him; a hat, a coat and an umbrella.
✔  He took with him a hat, a coat, and an umbrella.*

* The serial (or "Oxford") comma after "coat" is optional. Writers and editors have varying opinions as to whether it should be used or avoided. It can resolve ambiguity, but also create it. See here.

Grammar

Common grammatical errors are those relating to number, verbs, and pronouns. In the following pairs, the first one is incorrect.

✖  New Zealand are fielding a strong team. (incorrect)
✔  New Zealand is fielding a strong team. (correct)

✖  The ship sunk in a few minutes
✔  The ship sank in a few minutes.

✖  He bought it for myself.
✔  He bought it for me.

✖  Her and I went to town on the bus.
✔  She and I went to town on the bus.

✖  Just between you and I, he's lucky to have married her.
✔  Just between you and me, he's lucky to have married her.