Seymour, about things to do, i have noticed you're a young guy that lives the life, you'll feel yourself right on spot in Paris, enjoyed it differently every time ive been there, great city, def one of my favs in Europe.
places to chill, have a nice drink and a dinner i very liked Barlotti for a diner in a fancy place, Paul Chene for traditional, very nice french cuisine, Bristol same but with that Louis XVIII posh. Another typical French bistro is L'Avant Gout, great French atmospehere and very same cuisine. Bound, Buddha Bar (in London i liked it better but its still great) for a cocktail or 2 and some clubbin (must be said the cocktails are about $20 a pop) but its worth it. these are from the same owner and they did a great job with all the different spots.
some cool nightclubs i like were Showcase (a big joint with electro music and a lots of french madames that love to party) Le China (a bar, club, restaurant with leather couches and dark interior, very cool place with an oriental kitchen that is worth checking out), L'Etoile is also ok, Batofar a club on a lighthouse boat on the Seine.
sight seeing is easy in Paris, just walk down the streets and enjoy the views. of course some things you gotta do in the city is visit the top of the Eiffeltower, i would recommend a cruise on the Seine, especially if you're with a lady you both will enjoy it and see great spots of the city. that list mr.Teaser put up is pretty much spot on.
there's a lot of things to do in Paris, enjoy your time man!