First thing : It's not easy to get TVA (sales tax) refund in France !
Who can get TVA refund ?
The refund of TVA is reserved for non EU resident of more than 15 year old. You 'll be spending less than six months in EU.
On what ?
There is no TVA refund on : food, tobacco, repairs, services and travels. You can only buy for personnal purpose and all must go in your luggages.
French taxes are 19,6%, but the refund is often12% (to cover the time and efforts of the shop).
On what conditions ?
The purchase goods must worth at least 175 € at the same shop in the same day. The shop must offer "vente en detaxe" ("Duty-Free") service. Present your passport at the time of purchase and ask for "bordereau de vente a l'exportation" (export sales invoice). Most of the luxury shop and the Grand magasins (Galeries Lafayette, Printemps, Bon Marché...) have a special Duty-Free desk.
The "bordereau de vente à l'exportation" has four pages, one kept by the shop, a yellow one for customs services, a pink one you will have to post with the self-adressed enveloppe provided by the shop, and a green one, your receipt. As you leave France or any EU country, show your purchase goods and have the three pages stamped by a customs official at the departure airport. This can take some time, so count it in your arrival at the airport. The fund transfert can take fex months !
See the website (in french): www.douane.gouv.fr/page.asp?id=416
You can download: a PDF file with the explanations in English and Spanish.