Infinitives

The infinitive form of a verb can be used as a noun, adverb, or adjective. An infinitive can be in the present or present perfect tense (to throw, to have thrown) and in the active or passive voice (to throw, to be thrown).

Split Infinitives

Traditionally, grammarians forbade placing any words between the word to and the verb stem in an infinitive. Most experts now allow split infinitives, especially when not splitting an infinitive creates an ambiguous or awkward construction.

Awkward: We want to increase profits on our hardware products substantially.
Better: We want to substantially increase profits on our hardware products.

Omitting To

The word to may be omitted when an infinitive follows certain verbs, including help:

I will help mow the lawn.

Infinitive-Gerund Confusion

Do not mistakenly use an infinitive in place of a gerund (present form + ing).

Incorrect: She had the privilege to give him the award.
Correct: She had the privilege of giving him the award.

English idiom dictates which form is correct. If in doubt, phrase your sentence with the infinitive and with the gerund, and use the form that sounds most familiar in that context