Impressions of Paris depend heavily on why you are there: As a tourist, its a wonderful place, full of culture and life. If you live there as I have done for the past 5 years, your point of view can become a little jaded.
You are probably reading this as a future tourist, so I will enlighten you on some of the basics and highlights of this capital city: Very few people go to Paris without seeing the Eiffel Tower, and rightly so; It is a masterpiece of construction, originally a temporary structure, it dominates the skyline with its grandeur. This year it retains its lighthouse beam feature (as intented by Eiffel), and the council have decorated it in little blue lights. Very pretty. Try to pluck up the courage to venture to the top, as the view is breathtaking and its the perfect place to propose to your loved one.
Another must is Sacre Coeur (sacred heart) at Montmartre; A deceiving church as it was only built at the beginning of the 20th century and is in fact made of concrete (one of the first in Europe). Another splendid view over Paris and midnight mass is magical. This is the only place I know that has a glass confessional box, so all can see you as you repent!
Other sights are the Champs Elysees for seriously chic shopping, La defense for the buisness minded, Napoleons Tomb for a bit of pomp and Bastille for the new opera house and groovy shops.
For art and culture, top of the list is the Louvre and the Pompidou Centre, but if you want to discover some up and coming artists, then I suggest you go to the back streets of Bastille - there are some fine venues here.
For nights out, I suggest the Rex club in the 2nd quarter; Try and avoid the Irish and English pubs unless you really need the home comforts of sky sport, a good pint and a bag of salt and vinegar crisps - in short supply elsewhere in Paris (The only one I would recommend is Connellys Corner near the rue Mouftar).
Restaurants are rife in Paris: Japanese is pretty cheap, Chinese the same, but dont be suprised if sweet and sour pork with egg fried rice are not on the menu. Your best bet is African - good food at good prices. For cheap and filling try the Fouta Toro on the backstreets of the 18th, or the classy 404 in the 11th. The best French cuisine Ive come across is Rendezvous les Chauffers on rue des Portes Blanches, 18th.
For shopping, well Paris was made for shopping, the best tip I can give here is the coolest place in town, for the moment, Raglight, a second hand clothes shop on the Boulevard Barbes, 18th.
Paris is seperated into 20 arrondisments, most of the places you will be visiting will be between the 1st and the 9th. Try and be a little adventurous, as nowhere is really that far from anywhere else in Paris. Metro is the best form of transport (far superior to the London Underground), traffic on the roads is appalling, so try to avoid the buses unless you really have to.
If you want to live and work in Paris, then pick up a free copy of Fusac (available at most anglo orientated outlets), and if you are serious about it, then contact me so I can give you the lowdown on the piles of paperwork you will have to fill in.
Whatever your reason for visiting, I wish you lots of fun and a most excellent time.