To vs Too vs Two
This is a big one. I see this mistake all the time, way more than would typically be expected from typos alone.
“To” is one of the more widely used words in the English language and has eight million several different definitions and parts of speech. In its most common contexts, it is used as part of infinitive verb phrases, such as in “to eat” or “to go,” and as a preposition with widespread connotations, such as in “Let’s go to the store,” “Give it to me,” “The Cubs are down 84 to 11 to the Pirates,” or “To this day, I hate mushrooms.” Think of it as the default of the two.
“Too,” on the other hand, is different. It can mean “in addition,” as in “I want to go, too!” or “You two hate to eat mushrooms and onions, too,” or can refer to excess or degree, as in “You are too funny!” “I drank too much last night,” or “Tom wasn’t too amused by Hannah’s theatrics.”
“Two” is simply the number 2, exclusively. (On a related note, in formal writing, numbers between 0-10 (some say 0-9, but it’s a typically a matter of preference) should be written out, as in “I have two siblings,” “There is zero doubt in my mind,” or “I was ten-and-a-half when the younger of the two was born,” while larger numbers are typically written in numerical format, as in “There are 8,459 other things I should be doing right now,” or “Dude, I like totally drank like 12 beers last weekend.”)
When in doubt, use “to,” but remember that if you’re meaning to say “in addition” or “to an excessive degree,” use “too.” If you’re referring to a numerical amount, use “two.”