"Into" vs "In to"

WHAT???

You mean to tell me there's a difference between the two?
Ah...yes, there is. Now, before you start panicking, let me be honest. You probably already know the difference. And you probably don't mistake "into" for "in to". But, just in case, I'll give you this grammar lesson:

"Into" is a preposition which is often used to answer the question "where?". For example:

"Where are Jack and Jill?"
"They went up the hill."

Oh, wait...that won't work. LoL. Let's try that again.

"Where are Dick and Jane?"
"They went into the book."

Or something like:

"The dogs ran into the woods before realizing they were chasing a gust of wind." Silly dogs. ;-)

The "where" in the sentence is "into the woods".

Or "Into" is used as an analogy in time or when you speak about math. Like the following:

"It's well into November and the leaves haven't fallen off the trees yet."
"Six goes into twelve twice."
Basically, "into" is used A LOT.

The only time you actually use "in" and "to" apart is when they accidentally find themselves next to each other in the same sentence. They are "neighbors", but don't belong together. They actually belong to the word before or after them instead. Like this:

"The fireman ran in to get the dog out of the burning house."

"In" in this sentences belongs to ran and "to" belongs to get. In these sentences "in to" mean "in order to". Makes sense? Here's another one:

"The bird flew in to grab his jacket."

Now, for these two examples you could easily switch them up and write "into" instead. Like this:

"The fireman ran into the burning house to rescue the dog."
"The bird flew into the cage to grab his jacket."

Just and for your information...I like the "into" sentences better.

And apparently, there are also lose English (60's colloquialism apparently), that allows "into" to mean "deeply interested or involved in". You would use it the following ways:

"My daughter is heavily into her horses."
"The President is looking into the matter."

According to some grammars, this is not acceptable English, yet its acceptable in "informal communication".

That's it!
From: http://justine-dell.blogspot.com/2010/06/grammar-police-into-vs-in-to.html