This is great, spelling and pronunciation lessons!
A few of my pet-hates:
Their/There ('their' indicates ownership, e.g their bikes, 'there' indicates location, "over there")
They're, We're, You're etc, all these words are 'conjunctions', that means they combine two words, e.g "We are here", 'were' indicates past tense, "they were here". Another example, "You are silly", 'your' indicates possession, e.g "your fish are nice". Just always think when you write it, should it be "you are... bla bla" or does that sound wrong? In that case it's probably "your" you want.
Angles/Angels!!! How many degrees are your angles?