Learn it right!
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There is usually used to describe a physical place or location, or at least a noun. It can also be used in other ways, but I don't know how to best describe it. The following examples should help:
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- Over there is my brain!  I left it on the side of the road.
 
- There exists a time when every man must learn his homonyms.
 
- Do you see now that there is a difference?
 
Their is used to show possesion.  Just as 'his' shows possesion
of an object by 'him', and 'her' shows possesion of 'her', their shows
possesion of an object by a group, they.
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- It's their crap, not yours.
 - Their idea to teach people homonyms was wonderful.
 
They're is a contraction of the words "they" and "are", as indicated
by its apostrophe.  You use it to describe a group of objects or whatnot.  If
your sentence doesn't sound right by replacing they're with they are, 
then you're using the wrong form of there/their/they're.
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- They're stupid; they don't even know their homonyms.
 - It's good that they're reading this page though.
 
To is hard to explain.  It's kinda like an implied verb prefix.  Read the examples.
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- To be, or not to be, that is the question.
 - I have to go to the bathroom.
 - You want to go to the concert with me?
 
Two is the spelling of the number 2.  Use it when referring to
2 elements of something.
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- There were two ducks in the pond, not three.
 - What do you call a blonde with two brain cells?  Pregnant!
 
Too can mean either 1) also, or 2) an excess of.
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- I have to go to the bathroom too.  (case 1)
 - You go to the bathroom too much.  (case 2)
 - Hey, I want some beer too! (case 1)
 - You are too young to go in the bar!  (case 2)
 
Are is hard to explain also.  Read the examples.
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- Are you going to the concert?
 - There are five ducks swimming around the pond.
 - I bet you are tired after that long drive!
 
Our shows possesion.  Use it when you are referring to a group
you are in that 'owns' something.
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- Hey, that is our money, don't touch!
 - Our pineapples are the best in town.
 - Would you like to tour our factory?
 
Your shows possession.
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- Is this your money sitting here?
 - Can I have some of your Coke?
 
You're is a contraction for "You Are".  If you can't replace
you're with you are and have your sentence work, then you've messed up.P?>
- After that run, I bet you're tired as hell.
 - Hey baby, you're pretty hot.  (don't try this one in real life)
 
Its is the possesive form of it.P?>
- The vase lost its shine over the years.
 
- It's going to be a nice day today.
 - Come inside... it's raining!
 
- Your pretty nice to help us invest are money like that.
 - You're pretty nice two help us invest our money like that.
 - Your pretty nice to help us invest are money like that.
 - You're pretty nice to help us invest our money like that.
 - You're pretty nice too help us invest are money like that.
 - Your pretty nice to help us invest our money like that.