Using commas correctly
Our friend the comma can sometimes catch us out. If we're separating two independent clauses then we don't need one. Look:
The boy ran for the bus, he was really late.
We shouldn't be using a comma there - that's called comma splicing, and it's wrong. Here's why - both clauses make sense on their own and could be written as two separate sentences:
The boy ran for the bus. He was really late.
They make sense as two sentences. Alternatively, they could be joined using a conjunction, like this:
The boy ran for the bus because he was really late.
The other option (and this is the fancy one) is that you can separate two independent clauses with a semi-colon:
The boy ran for the bus; he was really late.
Now we're cooking with gas - this is rather sophisticated.
If you want to find out more about how to use commas correctly, visit this site:
http://www.bristol.ac.uk/arts/exercises/grammar/grammar_tutorial/page_07.htmIt
It has some really clear examples and some great exercises to do to test your knowledge.