Oh, man. How about ending a sentence with the word "at?" I mean, yes, ending sentences with prepositions is bad, but when the line "Where are you at?" shows up, I honestly want to hurt someone. There is no need for the final word! "Where are you?" is a perfectly acceptable sentence!

Or It's/Its! It's: it is; its: possessive.

It's easy: your, their, its - possessive all, and not one apostrophe.

My little grammarian heart is jumping for joy at this post!