Turnip Trading with Friends
If you and a friend adjust your console Time/Date settings and find an arrangement where one of you can buy cheap Turnips and the other can sell them at a tidy profit, you can buy as many Turnips as you can afford (up to 1000, to fill a storage bay) and then travel to your friend's town to sell them for a huge profit. Repeat the process as often as you like.
If you want to collect golden furniture, you must acquire three gold nuggets (acquired from the fake rocks) and 10,000 bells. Visit Cyrus at Re-Tail with the loot in hand. He can turn them into a piece of golden furniture, though you can't specify which piece he'll build so it could take a while to complete a proper set.
Happy Home Showcase
The Happy Home Showcase is a Streetpass area that you can access once you pay off your first house loan, which comes to a total of 10,000 bells. Once you talk to Tom Nook after doing so, he'll walk you through using the ATM and you can meet Isabelle's younger brother, Digy. You'll find him near the arch in Main Street.
You can unlock additional locations within your village by satisfying certain conditions, as indicated below. If you have satisfied the conditions as stated and the new location does not become available, wait a few days. Some places will not appear until you have been living in the village for 7 to 10 days, or there may be an additional time restriction after you meet the other criteria. Most buildings must be obtained through the Public Works.
Club LOL - Upgrade Nookling Junction at least once, give Dr. Shrunk permission when he visits, and obtain signatures from six villagers
Dream Suite - Visit Isabelle, who should be asleep in the Town Hall
Fortune Teller Shop - Have your fortune read 20 times by Katrina, the visiting fortune teller, then talk to her again and the shop will become an option
Garden Center - Plant or water 30 plants or flowers/trees, or pull 30 weeds
Kicks - Spend over 8000 bells in the Able Sisters' shop
Museum Shop - Donate at least 20 items (with one or more in each category) to the museum, and talk to Blathers daily
Shampoodle - Spend at least 10,000 bells in Able Sisters' or Kicks and then wait at least 10 days after Kicks is built
The Island Resort - Upgrade to a house, then talk to Tortimer at the docks and you can visit the island a day later
The Roost Cafe - Donate 50 items to the Museum, and unlock the Museum Shop, then talk to Blathers 7 days after the shop's grand opening
There are four mannequins you can unlock. The first three are unlocked by talking to Mable, Sable, and Labelle each day until you become good friends with each of them. You'll find the fourth mannequin once you purchase your first item from the third floor of the T&T Emporium building.
You can unlock the various gold tools by completing the corresponding requirements, as indicated below.
Shovel - Purchase 50 fertilizer packs from T&T Emporium
Fishing Rod - Catch every type of fish and talk to Chip at the next fishing tournament
Net - Catch every type of bug, then talk to Nate at the next Bug-Off
Watering Can - Receive and maintain a perfect town rating for 15 days in a row, then talk to Isabelle about the town rating at the Town Hall
Axe - Purchase 50 tree saplings from the Gardening Shop
Slingshot - Shoot down 16 balloons and it will appear in the air, suspended by three gold balloons
Become friends with Sable by talking to her every day and eventually a QR machine will become available for your use inside The Able Sisters building.
You can acquire the various silver tools by satisfying certain requirements, as indicated below.
Shovel - Donate 15 fossils to the Museum, then buy it for 500 bells when it randomly appears on sale on the building's second floor
Fishing Rod - Donate 30 fish or sea creatures to the Museum, then buy it for 500 bells on the building's second floor
Net - Donate 30 bugs to the Museum, then buy it for 500 bells on the building's second floor
Watering Can - Purchase 50 or more flower seeds
Axe - Randomly available on the island, in exchange for 8 medals
Slingshot - Shoot down 16 presents, then shoot down the slingshot (held aloft by two silver balloons)
Tips and Tricks
You can avoid having to deal with bees when you shake trees. To do so, open your town gate to allow people to visit. Now you can shake trees for furniture, bugs, and bells without the risk of running into an angry swarm.
Rotten Fruit Disposal
If you're stuck with rotten fruit, normally you would have to pay to dispose of it at Re-Tail. However, an alternate option is to plant the rotten fruit to produce a sapling, which you can then dig up and remove. That technique saves you the cost of disposal.
Reggie Comes To New Leaf!
When you visit the HH Showcase, you may be able to check out the house that belongs to Reggie Fils-Aime, a Nintendo employee. His profile indicates that he lives in West 12. His house has a yellow roof and his interior contains familiar Nintendo content.
The easiest way to get bells in the game is to visit the Island Resort after nightfall. When you leave the hut, you can talk to the gyroid and he'll let you borrow any tools that you need. Using the net, you can capture beetles that appear on trees there. While you are on the island, you can gather more insects than you would usually be able to carry, then take them back to the mainland and make several trips to the store. The golden stag beetle is worth 12,000 bells at Re-Tail, and other insects fetch a similar price. If you want to improve the rate at which valuable insects spawn, you can...
Look around your town for fruit trees of the variety that are native to your town. Next, look for trees that drop fruit of a different color. When that happens, plant that fruit and it will grow into a "perfect" tree. That tree's fruit can be sold for a larger than normal profit, though eventually the tree may stop producing its special fruit and the value of its yield will significantly decrease. Still, you can enjoy the perfect fruit while it lasts!
You can wake up Cyrus. To do so, you need to sell items to Reese totaling 100,000 bells or more. You must also have 100 or more things in your catalog, and 7 or more days need to ahve passed since you started your game's file.
You can receive pictures of your neighbor animals by either becoming good friends with them (by performing tasks for them and interacting them in a positive way on a regular basis), or by playing the event on April Fool's Day. During that event, if you pick the fake copy of an animal, you'll receive a picture of the real one.
Animals have a tendency to move into places in your town that you might be saving for something neat. If you have something in mind for a plot of land, mark your territory using some custom signs. Then you can just remove them when you're ready to actually build.
Mushrooms From Stumps
If you cut down a tree and you notice some symbols on the stump, don't dig it out like you normally might. Leave it where it sets for a few days and mushrooms will start growing from the stump.
Make sure to sell your stuff at Re-Tail when you have the opportunity, rather than at the Nook stores. Re-Tail will offer more bells for items you sell. For example, your fruit can sell for 80 at a Nook store, but sells for 100 at Re-Tail. That's a 25% price increase in your favor.
You likely already know about the special rock that appears somewhere in your village every day, which produces money when struck with a shovel. However, there's also another rock that breaks when you hit it and leaves behind a special piece of ore or a gem (like a ruby), which you can then sell for a good price. Hit the rock with a silver shovel and you may be able to acquire as many as nine gems in one day.
More Money From Rocks
Every day you play the game, there's a rock that contains some hidden bells. You can whack the rock with a shovel to send some bells flying. Repeated hits during a limited time period will allow you to gain additional bells, but normally the number is limited somewhat by the step you automatically tack back after whacking the rock. One way to fix this is to stand against a rock, then dig holes to your left and right, as well as behind you. Now when you hit the rock, it won't send you flying backward. You can whack it more frequently to produce additional bells before the invisible timer expires, handily increasing your total earnings.