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

GRAMMATICALLY CORRECT
adverb) between the to and the verb: to loudly bellow, to peevishly
whine, to cleverly connive, to boldly go.
For reasons inscrutable to many today, nineteenth-century grammarians
decided that some of the rules of English grammar should
conform to those of Latin. In Latin, the infinitive is not split; ergo,
in English the infinitive should not be split. (The fact that in Latin
the infinitive is one word and therefore can't be split didn't seem
to trouble the rule makers.) The result is a decree that presents the
modern writer with a dilemma: Should one ignore it, since breaking
it usually does no real harm, or follow it, since failure to do so may
be taken as ignorance?
There is obviously no definitive answer to this, but given the
widespread adherence to this convention, it's probably advisable to
abide by it within reason. That is, if it's just as easy to word something
in a way that avoids splitting an infinitive, do so-if for no better
reason than some of your readers will fault you otherwise. For
example, rather than saying Their greatest pleasure was to proudly
stroll along the boardwalk with their pet armadillo, you could
put the adverb after the verb: Their greatest pleasure was to stroll
proudly along the boardwalk with their pet armadillo. Sometimes
the adverb must go in front of the to: Instead of I wanted to never
see him again, you could say I wanted never to see him again.
In fairness, an infinitive does sometimes function best as a unit,
and separating its parts can weaken it by putting undue emphasis
on the intervening adverb. And certainly, even if you have no problem
with splitting infinitives, don't shatter them. Constructions such as
the following seriously interrupt the flow, and make comprehension
difficult:
260
She knew it would be a good idea to before the job interview grow out
the green Mohawk.
BETTER: She knew it would be a good idea to grow out the green
Mohawk before the job interview.
He asked me to as soon as I was finished grooming my newts clear off
the table.
BETTER: He asked me to clear off the table as soon as I was finished
grooming my newts.