Well to be honest you haven't got long there have you? It's like trying to do London in 6 or 7 hours - just not possible! Decide on the one or two things that you REALLY want to do and just do them. For example, if I was going for such a short time, and I'd never been before then I would probably head straight to the Eiffel tower (though it will probably be really busy at that time of the day - first thing in the morning is a great time to go), then possibly to the Arc de Triumphe and maybe a quick stroll along the Champs Elysees.
But those might not be your first choices. Whatever you choose make sure you take the time to enjoy where you are and don't rush off to do too many things in too short a time.
Though of course you may prefer to do one of the tour buses, that way you'll see (if not visit), many of the main sites.