Grammatically Correct: The writer's essential guide to punctuation ...

GRAMMATICALLY CORRECT
The critics hated it, the public loved it.
I doubted she would show up, she was so unreliable.
WHEN AN INDEPENDENT CLAUSE IS PRECEDED BY ANOTHER
ELEMENT, PUT A COMMA AFTER THE INTRODUCTORY ELEMENT
An independent clause may be preceded by a dependent clause, a
phrase or a single word.
DEPENDENT CLAUSES
In the following examples, the dependent clause appears in italic
type.
Whenever you're ready to eat, the dining table will be cleared.
Whenever you're ready to eat the pie, I'll take it out of the freezer.
If you have finished, your wine waiter will be happy to make a suggestion
for a digestive.
If you have finished your wine, may I pour you some tea?
Although I'd love to stay to help clean up, I just remembered nine urgent
appointments.
After the ceremony was over, the guests all leaped into the hot tub.
Because the weather was so bad, the Polar Bear Club held a special
mandatory swim.
Since you insist, I'll let my eyebrows grow back in.
When the phone finally rang, she hurled it out the window in a fit of pique.
Why the need for a comma? Just as with two independent clauses,
it may not always be immediately obvious from the syntax (word
order) alone when the first clause has ended and the next has begun.
For example, compare the first two examples above. In both cases,
the comma signals when the end of the dependent clause has been
reached-but this happens in different places. In the first case, the
action of eating is unconnected to any object; here, the first clause
is complete right after the verb eat. In the second case, the action
of eating applies to an object (pie), and here the first clause is not
complete until the recipient of the verb is identified. Suppose you
omitted the comma in the first sentence:
66
Whenever you're ready to eat the dining table will be cleared.