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

PUNCTUATION
If no comma appeared after eat, the reader might momentarily
expect that the sentence will go on to identify what was eaten. This
expectation, however, will cause the sentence to fall apart, turning
its first part into Whenever you're ready to eat the dining table (!),
and the remainder into a meaningless string. Faced with this nonsense
syntax, the reader must go back and reassess the sentence to
make sense of it. The comma eliminates any possibility of confusion.
PHRASES
Just as with dependent clauses, when a phrase comes first in a
sentence, readers need to be shown precisely where it ends and the
main clause begins.
In the following examples, the phrases are shown in italics.
According to his study, people want more say in how the weather is
forecast.
To see the fall colors at their best, try taking your Blues Brothers shades off.
Leaning over the balustrade, we could just see the runaway merry-go­
round horse plow into a huge display of Kewpie dolls.
At the age of eighty-three, Irma took up snowboarding.
Beginning at dusk, the frog sentoutacall of apparently unrequited passion
all through the night.
Reading being her obsession, Katie's first act upon starting her sentence
was to find the prison library.
Struck by a sudden idea, he feverishly began to learn Ancient Greek.
Next to synchronized swimming, mud wrestling was her favorite sport.
Note that a phrase itself is not subdivided by commas, because,
like a clause, it may be considered a unit.
INTRODUCTORY WORDS
A single word can also serve to introduce an independent clause.
Therefore, it just won't be possible to finish building the opera house in
time for the first act.
Understandably, she's reluctant to take on the responsibility of escorting
a dozen fourteen-year-olds to Las Vegas.
Piqued, he went back to polishing the bedsprings.
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