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

GRAMMATICALLY CORRECT
BETTER: Her responsibilities were to manage the PR department and to
attend trade shows.
OR: Her responsibilities were the management of the PR department and
attendance at trade shows.
A computerized database index needs to be reorganized when it has
become fragmented, or to correct the skewing of values.
The focus switches from what is happening to the database index
to what the person using it should do. Since the subject of this
sentence is the database index, not the user, the passive voice is
more appropriate. (For more on this, see "Active Versus Passive
Voice" on page 286.)
BETTER: A computerized database index needs to be reorganized when
it has become fragmented or when its values have become skewed.
She told him to get to the hotel by six o'clock, that he should check with
the concierge for messages, leave his luggage at the front desk and to
wait for her in the lobby.
The same wording must be used for each element. Repeating
that he should four times would be clumsy; to is better. If to is
used, it must be put either before each element in the series or just
at the start.
BETTER: She told him to get to the hotel by six o'clock, to check with
the concierge for messages, to leave his luggage at the front desk and
to wait for her in the lobby.
OR: She told him to get to the hotel by six o'clock, check with the
concierge for messages, leave his luggage at the front desk and wait for
her in the lobby.
The consultant objected to the proposal, saying that the costs would be
exorbitant and because the training facilities were insufficient.
There is no reason to switch from that to because. In addition
to the faulty parallelism, note that this slightly changes the meaning,
turning the consultant's second objection from a matter of opinion
to a statement of fact.
BETTER: The consultant objected to the proposal, saying that the costs
would be exorbitant and that the training facilities were insufficient.
It would also be acceptable to drop the second that, since it can
be inferred.
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