When searching for the proper usage of the words "in to" and "into", I found a useful reference site called Dictionary of Sound-Alike Words. You wouldn't believe how many emails I receive (and write) every day that use basic English words incorrectly.
Here's how the Dictionary of Sound-Alike Words lists "in to" and "into":
in totwo words, an adverb and a preposition, as in: Even though it was supposed to be her day off, she came in to finish her monthly report.
intoentering or changing form, as in: She drove into the parking lot and found a space.
