When a coordinating conjunction connects two or more independent clauses a comma must precede it. A comma tells readers that one independent clause has come to a close and that another is about to begin.
EXCEPTION:If the two independent clauses are short and there is no danger of misreading, the comma may be omitted.
TIP:As a rule, do not use a comma to separate coordinate word groups that are not independent clauses.
The word group following and is not an independent clause; it is the second half of a compound predicate. The two parts of the predicate belong together, so do not separate them with a comma.
Exercises:
Major uses of the comma 1
Major uses of the comma 2
All uses of the comma
Related topic:
Unnecessary commas with compound elements