1 The Mistake:
"Will you call me tomorrow"?
"Will you call me tomorrow?"
All punctuation must go inside the quotation marks.
2 The Mistake:
I went to the market, I needed some fruit.
I went to the market; I needed some fruit.
I went to the market, because I needed some fruit.
Two independent clauses cannot be joined by only a comma. A semi colon is needed, or a comma and a conjunction.
3 The Mistake:
I was hungry so I ate a sandwich.
I was hungry, so I ate a sandwich.
When two independant clauses are joined, a comma and conjunction is needed.
4 The Mistake:
More than one exclamation mark should never be used.