When you first move into your village, there will only be a few shops open. You can upgrade and add some new shops if you know how to unlock them.
You can upgrade the item shop so it sells more items. You do so by spending bells at the item shop and doing a few other things. Only items that can be sold out count toward your total. In other words, stationery, wrapping paper, and melody cards don't count toward the bell total. Fortune cookies are counted as 500 bells.
To upgrade to the convenience store (T&T Mart), you must have a house rather than a tent. Upgrade from the tent by giving 10,000 bells to Tom Nook. The convenience store upgrade occurs after 12,000 bells have been spent in the shop (all players on the game card can contribute) or you have bought at least 15 items. It must be at least 10 days since you created the town.
The supermarket is called Super T&T. The supermarket upgrade occurs after you have spent 25,000 bells in the shop. It must be at least 10 days since the convenience store opened. It must be at least 10 days since the garden center opened.
The upgrade to the home center (T.I.Y) occurs after you have spent 50,000 bells in the shop. It must be at least 21 days since you built the supermarket.
The upgrade to the department store (T&T Emporium) occurs after you have spent 100,000 bells in the shop. It must be at least 30 days since you built the home center. You also have to pass Gracie's fashion check at least four times before the emporium will open.
To unlock the garden center, the total number of times you have done any of the following actions must be at least 30: pulled weeds, watered flowers, planted trees or flowers. If you don't have a watering can and haven't earned 100% approval rating (see the starting the game guide for information about increasing your approval rating), talk to Isabelle at her front desk in the town hall and ask for advice. If you do all of the things she asks, she will eventually give you a watering can. You can also get a fishing rod or bug net if you keep asking her for advice.
Nook's Homes is open from the beginning. Once you pay off your down payment and get a house instead of a tent, Nook's Homes will start selling exteriors, such as new roofs, mailboxes, and so on.
After you pay off your first home loan using the ABD in the post office, talk to Tom Nook. Then exit Nook's Homes and go back in. Tom Nook will introduce Lyle, who will give you advice about increasing your HHA score.
If you're still living in a tent, pay off your down payment by giving 10,000 bells to Tom Nook. Then use the ABD in the post office to pay off your first house loan. Be sure to talk to Tom Nook after that. The Happy Home Showcase will open the next day.
Donate at least 20 items to the museum, with at least one from each category (bugs, fish/deep sea fish, fossils, works of art). Then talk to Blathers each day. One day, he will be thinking about something. Talk to him and he will talk about the museum shop. After that, the museum shop will be added to the list of things you can build in your town. Just sit in your mayor chair and ask to build something, then choose the museum shop.
In the Able Sisters' shop, you can unlock a QR code machine that creates a QR code that represents a custom design. Other players can then scan this code to get your custom designs into their games. To unlock this, talk to Sable, who is working at the sewing machine. You have to talk to her each day for several days in a row. Then the QR code machine will be unlocked.
For Club LOL to open, your shop has to be upgraded to the convenience store, and you have to have reached 100% approval rating according to Isabelle (see the starting the game guide for information about increasing your approval rating). Then the next day that you play, Dr. Shrunk will be outside of your house and will ask you to get signatures for his petition. Agree to do so, then talk to six of your villagers and ask them to sign the petition. Once you have six signatures, go talk to Dr. Shrunk in Main Street to give him the petition. The next day, Club LOL will open.
Spend at least 8000 bells in the Able Sisters' shop to unlock the shoe store, Kicks. It must be at least ten days since the town was created.
Spend at least 10,000 bells in Able Sisters' or Kicks. It must be at least 10 days since Kicks was built.
Katrina is the fortune-telling cat who sometimes shows up in your town square. To unlock the fortune teller shop, Katrina needs to tell a total of 20 fortunes while in your town. You can have friends come over and have their fortunes told to increase the number of times she has told a fortune while in your town. After she has told 20 fortunes while in your town, the mayor of the town has to talk to her. When this happens, the fortune teller shop will be added to the list of things you can build in your town. Just sit in your mayor chair and ask to build something, then choose the fortune teller shop. Lloid, the fundraising gyroid, will be in the train station to collect donations for the fortune teller shop.
The Dream Suite is a place where you can visit dream versions of towns, where you can do whatever you want without affecting the real town. After you been mayor for seven days, go to the town hall. If Isabelle is sleeping, talk to her. This unlocks the Dream Suite in the list of public works that you can build.
Donate at least 50 items to the museum, and open the museum shop (see above). After the museum shop has been open seven days, talk to Blathers. He will eventually be thinking about something when you go into the museum. Talk to him at that time to add the Roost Café to the list of community projects.