People who use atrocious grammar really annoy me. Now, I am the first to admit that I don't use perfect grammar myself sometimes, and I do use slang. But there are some things that you just need to fix if you are still making these mistakes. So here are a couple of hints:
The Difference Between "their," "there" and "they're":
Their-used as a possessive pronoun. For instance, "Did everyone get their lunch?" When talking about making, doing, or belonging to more than one person.
There-usually used as a non-specific location for a place. For instance, "Please go sit over there." This word is usually used to cut down on description so that your sentence isn't cumbersome. When speaking, "there" is usually used in correlation with a pointed finger toward what you are talking about: "Please go sit over there (points to chair at the table)."
They're-used as a contraction of "they are." This word is a plural noun's state of being. For instance, "They're painting my bedroom." What are "they" doing? They are "painting." The easiest way to remember when to use this word instead of the others is by taking it out of the contraction and seeing if "they are" fits just as well into the sentence, if it does then that's the one to use!
It Is "A lot," Not "Alot":
This is one that is so often misspelled you would think it's the right way to do it! I am constantly amazed at how often I have seen people use "alot" as one word. The most recent one was at my sister's place of work where there is a thank-you letter posted written by a 1st grade teacher saying her class "had alot of fun." People! "a lot" is two words, not one!
You're vs. Your:
I actually saw this one misused on a greeting card yesterday! UUUGH!!! This one has the same rules as the difference between "their" and "they're"...
You're-used as a contraction of "you are." This is a pronoun's state of being. For instance, "You're going to go visit Nana later, right?" What are "you" doing? You are "visiting." Same rule as before, take out the contraction and if you can put "you are" into the sentence without it sounding jacked up, then that's the one to use.
Your-possessive adjective, meaning of, belonging or done by you. For instance, "Your cat is a mean little thing, isn't she?" Who does the cat belong to? You.
It's or Its?:
Yes, a lot of mistakes are made with these tricky little contractions...maybe people would just be better off not using them. Seriously.
It's-a contraction of "it is." A pronoun that is used to refer back to something that was named before or as an impersonal pronoun. For instance, "The baseball just flew over the fence. It's the last one, can someone go get it?" Now, what's the last one? The baseball, we don't have to say that over (as in "The baseball just flew over the fence. The baseball is the last one...) because everyone knows what we are talking about at that point, and repeating it would just be redundant.
Its-possessive adjective, meaning of, belonging or done by it (a nonspecific noun). For instance, "I don't know what kind of animal it was, but its paw prints indicate a large animal."