Hmmm. I lived in Paris for a couple of monts, and in France for a couple of years. Unfortunately, Im not the biggest fan of Paris.
Beware the dog-poop. Seriously. When getting an espresso, make sure to YELL out good day one cafe please, and when you're done, YELL out thank you very much and au revoir.
Montmartre is a nice view I suppose (think Amelie, but not quite that pretty, ok?). But the 18th district is not very exciting. The 16th is the richest area. I think being central would be best on short time. You don't want to have your strongest memory being crammed with funky smells in the metro. If you ar central, you can walk a lot. Bring good shoes for it. I also recommend a map like
this, but that's an old version. They should be very affordable and found at any major bookstore there I imagine. The maps you pick up for free at hotels are missin waaaay too much.
The cemetaries are kinda cool. There's pere lachaise (sp?) and montparnasse. Well, the first is much better with Chopin, Jim morrissey replete with cigarette butt offerings, Oscar Wilde with his balls knocked off. Lesser known musical greats like Fournier, Robert Casadesus (whose wife I saw crying over his grave). wow this is morbid. My favorite grave was Alekhine's at montparnasse, even if he was an unlikable nazi sympathizer. One of the great chess greats. Whatever, cemetaries are not really worth going out of your way for I suppose.
If you want to see what eating in the most crammed conditions are, check out Chez Papa. I would go there when I needed something closer to american sized portions on a student type budget. Its sardine packed though.
The most beautiful things about France that I ever saw were the Alps and Bretagne. The latter is always rainy, but on a non-rainy day its somewhat surreal. There are no words for the Alps, that's coming from someone who's seen a fair share of national parks in the US. However, it takes times, perhaps a lot of driving, and best would be to know someone lucky enough to live in that area. Otherwise, unforgettable.
If I think of something, I'll let you know. Have fun planning!