a) A common error is joining two sentences or two independent clauses incorrectly with an improper punctuation mark instead of using a correct punctuation mark which is the semi-colon, or using a conjunction as the following example shows.
EXAMPLE: We don't have a telephone, you will have to come round to the house.
The two independent clauses in the sentence are incorrectly joined by a comma.

We can correct the sentence in the following ways:

• Treat the two clauses as separate sentences with the use of a full-stop (period) for each sentence.

  We don't have a telephone. You will have to come round to the house.

• We can use a coordinating conjunction (and, but, for, nor, or, so, yet) to create a compound sentence.

  We don't have a telephone, so you will have to come round to the house.

• We can turn one of the two clauses into a subordinate or dependent clause.

  Since we don't have a telephone, you will have to come round to the house.

• We can use the semicolon to create a compound sentence.

  We don't have a telephone; you will have to come round to the hous

EXAMPLE:
I helped them all I could, I even brought my tools to speed up the work. (INCORRECT)
I helped them all I could; I even brought my tools to speed up the work. (CORRECT)
I helped them all I could and I even brought my tools to speed up the work. (CORRECT)

b) A type of sentence error known as sentence fragment is a group of words that used together does not form a complete sentence.

• A dependent clause is being used as a sentence.

  INCORRECT: Because she was the best candidate.

  INCORRECT: Since ten o'clock this morning.

  CORRECT: She got the job because she was the best candidate.

  CORRECT: I've been here since ten o'clock this morning.

• The wrong form of a verb is used.

  INCORRECT: He eaten his lunch just a while ago.

  INCORRECT: He has showed her how to catch butterflies.

  CORRECT: He ate his lunch just a while ago.

  CORRECT: He has shown her how to catch butterflies.

c) Words and phrases should be put in their rightful places.