I have a one week trip next year to France. What would be some of the highlights I should try to see in the country while I am there?
When I had a week (about 7 years ago) we decided it wasn't going to possible to see "the key sites" in such a short time. So we took 2 days in Paris, 4 days outside, and then the last day back in Paris. The 4 days outside had a single theme. For us it was the Loire Valley and the chateaux. You might choose a specific wine region, or the Mediterranean beaches, or the Alps, or whatever. We saw the Louvre, the Eiffel Tower, the Champs Elysees and so on in Paris, took the train to Nantes, drove back up the Loire Valley seeing chateaux, eating, drinking and really soaking everything in until we reached Chartres, spent a day there, then the train back into Paris (DO NOT DRIVE IN PARIS) and enjoyed some more sightseeing there and headed home.
Think of the one non-Paris thing you'd like to focus on, and build a trip around that. I think you'll find it super memorable. If you aren't sure, look into the Loire ... we sure liked it!
There are so many things to see in France; one week is just too short.
As said above, something you can do is to arrange a "circular" trip beginning and ending in Paris, or directly arrive into another city. This way, you begin sightseeing the rest of France then finish by Paris.
If you want to begin your trip by a city other than Paris, there are two options available. Either you can get a connecting flight or transfer to a train that will take you to your destination. Check out flight combinations offered by Air France and other European airlines.
Choose wisely the cities you want to visit. I suggest you get a rail pass and chain cities which are 3 hours away max. from each other by train. Train trips between interesting cities in France average 2 hours. Allow several days in Paris, anyway. Yo are also free to experience driving on French autoroutes (freeways) and getting lost on countryside roads by renting a car; most intercity freeways have tolls depending on distance and you should be prepared to drive a stick-shift vehicle.
Here is a list of cities and interesting things to do there:
Lyon - 2nd French city after Paris, not far from the Alps, where 2 rivers join together and many hills in town
Marseille - harbor on the Mediterranean sea and 3rd city in size, where you can taste bouillabaisse (famous fish dish)
Montpellier - another sunny city close to the mediterranean beaches (short 10mn drive); you can find the beautiful gorges du Tarn going north
Toulouse - famous for the red-brick buildings and home of the French airspace industry; you can visit the Cité de l'Espace and, under certain conditions, the Airbus plant in which A380 is assembled. The Pyrénéres mountains (2nd mountain range after the Alps) are reachable from there by driving or train and bus combinations.
Bordeaux - a beautiful city of preserved ancient stone buildings, part of UNESCO worldwide heritage. Wine tours are available to visit chateaux and surrounding vineyards, including famous St Emilion. The Atlantic Ocean beaches, with their big waves and surfers, are 1 hour away by car or bus.
Take into consideration the train trip durations between the aforementioned cities :
Bordeaux : 3 hours (TGV)
Lyon : 2 hours (TGV)
Marseille : 3 hours (TGV)
Montpellier : 3 hours (TGV)
Toulouse : 5 to 6 hours by day service, better done by overnight train in which you can sleep in 4 or 6-berth rooms and arrive the next morning
There is an intercity train crossing the entire south of France: Bordeaux---(2 hours)---Toulouse---(2 hours)---Montpellier---(1.5 hour)---Marseille
Bordeaux to Marseille and further down the riviera to Nice is also available by overnight train.
Lyon-Montpellier : 2 hours (TGV)