Use commas after introductory
(a)
clauses, (b)
phrases, or (c) words that come before
the main clause.
Examples:
When I get hungry for Mexican
food (,) I head for Taco
Bell!
Because her Powerbook was broken
(,) she needed to rely
upon the computers in the school
lab.
Use commas to set off an
adverb clause that precedes its main
clause. Adverb clauses are begun by
subordinate conjunctions such as
after, although, as, because, if, since,
when, and while.
Example:
While I was eating (,)
the cat scratched at the door.
Note: Do not
use a comma when the adverb
clause comes after the
main clause:
Example:
The cat scratched the door while
I was eating.
Examples:
Participial Phrase:
Having finished the test (,)
she left the room.
Infinitive
Phrase:
To get a seat (,) you had
better come early.
Succession of Prepositional
Phrases:
After the test but before lunch
(,) I went jogging.