A particularly problematic set of triplets are the too/to/two's. Though I know the difference very well, I notice that I sometimes get too and to wrong when I am typing away and not paying attention. I go back through my work and discover that I have used one O instead of two; never the other way around.
Two is a number
"I have two blogs you can check out; one - All We Like Sheep (you are here) and two - my gluten free blog."
To has two uses
First, as a preposition, which comes before a noun
(a noun is a person - "A girl is typing this," place - "A girl is typing in a city," or thing - "A girl is typing this in a city on her computer."):
"Tomorrow I will go to church."
Second, as an infinitive, which comes before a verb
(a verb expresses action - to write, being - to be, or state - to sleep):
"We go to church to learn about God and to worship Him."
Too has two uses too
First, it is a synonym (means the same thing as) for also
"You can come too."
Second, it means over abundance
"People tend to have too many things that keep them from worshipping God."*
The way I remember the difference between to and too is to think that too is always talking about more: more things, more people can come, so it has more O's.
Stay tuned: there is more to come, Mordecai.
*This word has two acceptable spellings: worshipping or worshiping...no matter what your spell checker tells you.