To my skeptical English friends who don't believe that the French have good tea, I am on a personal mission to prove you wrong!
In the Marais area of Paris, down a little side street, which if you didn't know this place was here, otherwise wouldn't have drawn your attention, there is a little gem. It's a tea emporium called Mariage Frères, because of the founder, Monsieur Mariage, not because of any incestuous marital pacts that the waiters have to sign up to!
The first sensation upon entering is the smell of tea. You soon realise this is because of all the tea caddies lined up along the walls of the shop, from floor to ceiling, selling a vast range of loose teas for you to take home. There are some very knowledgeable sales assistants behind the counter, ready to help you make your choice.
(A word of warning: if you do make a purchase, they have a very old-fashioned way of taking your payment. You decide what and how much of it you want with the sales assistant. He will then give you a little receipt, which you take to the person at the caisse (cash desk) to show them what you've ordered. You pay the cashier, who will give you another receipt to take back to your original sales assistant to show you've paid, who will have prepared your tea for you. This procedure is not at all clear if your French isn't all that good!)
The next thing you might notice is a queue of people waiting to be seated in the small restaurant area towards the back. This place can get busy, and I don't think I've ever been there and not seen a queue for a table. However, it is definitely worth it! They do also do lunches and very extravagant afternoon teas, but my friend and I just had a pot of tea each with a slice of cake and that was absolutely perfect for us.
(Another word of warning: if you're used to English afternoon teas, this may not quite meet your expectations on the first impression. The waiters' linens may have a few creases, and the service isn't as stuffy, but for the variety and quality of the tea available, it's insurpassable! So much care has been put into the temperature of the water, the amount of time for steeping and the insulation around your tea pot to keep it warm. If you're daunted by the tea menu, all the waiters are trained "sommeliers" and can describe each tea in minute details so don't be afraid to ask for help!)
If you do visit this place, be sure not to miss the little Tea Museum upstairs - the steep stairs are tucked away, on your left as you come in. The museum only has two little rooms, but it makes you feel like you've gone back in time with all the tea pots and caddies etc. Actually the whole place has a very colonial feel... as we left and stepped out onto the street back into the Parisian rain, I felt distinctly like I'd just come back from an exotic holiday. You know that feeling when you've unwound and feeling really relaxed, but you arrive back at Heathrow, welcomed by sheets of rain...?
The shop that I have been to most is the one on rue du Bourg-Tibourg in the 4th arrondissement... but it is useful to know that they also have a branch in the Louvre (near the inverse pyramid), one on the Place de la Madeleine, and another in the 6th arrondissement on rue des Grands-Augustins.