The great thing about chains is that they bring accessibility to everyone. Lattes and espressos have become mainstream thanks to Starbucks, for example. As far as I know, there are not very many chain tea shops (I'm speaking about store fronts here) in the United States. I know of a couple of local chains, like New England's Tealuxe, but the only major chain that I am aware of is Teavana.
Teavana is a great place to get started if you are new to the world of loose tea. The advantage to being able to go to an actual shop is that you aren't just looking at pictures of the leaves, you can examine the leaves in person and smell them, maybe even try a cup. While there are plenty of other teashops out there, sometimes they can be hard to find. But, there is Teavana.
Teavana stocks over 100 teas, including white, green, oolong, black, and rooibos and herbal tisanes. They carry many favorites, as well as a few more exotic brands. Many of their teas are delicious.
However, there are a few caveats. Employees are encouraged to make sales, first and foremost, and so sometimes there is pressure to get the customer to buy as much as possible, something that is avoided with online shopping. So how to get the best experience out of Teavana (and possibly other tea shops as well)?
Behold!
The Teavana Shopper's Guide
1. Preparation: If possible, have some idea of what you are looking for before setting foot in the shop. This can be done by perusing the website. Look for teas that sound interesting to you and that you would be interested in smelling. Make a list before you get to the store!
2. Upon Arrival: When you arrive at the store, try the samples that they have available. But beware, many of them are prepared with German rock cane sugar, which the store also sells. So, if you're looking to cut back on calories, know that they will taste slightly different than if you were to make them with Splenda. (Rock sugar has a slightly different taste than granulated white sugar.)
3. How It's Sold: Tea is sold by the ounce (weight) with a minimum of two ounces of each tea. Therefore, if you tasted a sample that was a blend of two teas, you would be required to purchase four ounces total for tea. List prices are all for two ounces of tea.
4. Storage: Most likely, you will be encouraged to buy a tin for your tea. In the store, there are three sizes of tins: 6oz, 9oz, and 1lb, ranging from $4.50-$7.00. They are really great tins, with a double airtight seal. Having an airtight and lighttight container is vital for keeping your tea fresh for as long as possible. But, if you are buying two ounce quantities, you might not want a six ounce tin taking up room in your cupboard. On the website, three ounce tins are still available for $2.99. (They have been discontinued in the stores, except for a very expensive boxed set.) I would recommend getting the tin over the bags (which are free) because your tea will taste better longer, but know the tin sizes before you go, and know what you want.
5. Pound Discounts: If you drink a lot of tea, the pound discount is something to consider. When you buy a pound of tea, in any combination, you receive 10% off your total tea order. But, be careful. The pound price will be eight times the label price before the discount, and it can get expensive very quickly. I recommend this only if you drink several cups a tea a day, and are prepared to keep it in tins. There is also a five pound discount of 20%, but I would not recommend this for most people as this makes a whopping 1000 cups of tea! If you cannot consume that in a year, don't do it! You can also purchase the tea in 2 pound bags, but you only get the 10% discount once.
6. Tea Paraphernalia: Most of the drinks in the shop are made with the Perfect Teamaker, which is a great quick and easy way to make tea. There are similar versions put out by other companies, such as Adagio's IngenuiTEA. These are a great way to make a single cup of tea. For the less gadget oriented, a Swiss Gold filter works great as well.

The store also carries a wide variety of cast iron teawares. These are great for someone who wishes to invest in their hobby, and really spend a lot of time relaxing and enjoying a leisurely cup of tea. This is for the person who is pursuing the lifestyle of tea. Sometimes, however, better prices can be found shopping elsewhere. Search for Joyce Chen pots, as she is the manufacturer of many of the pots that Teavana carries.

7. Have fun! Enjoy your tea shopping experience, and don't let anyone pressure you into what you don't want. Tea is supposed to be a relaxing experience, not a stressful one. Try a cup of tea while you shop, and enjoy!
(Many of these tips would be helpful at other shops as well!)