There's quite a bit to learn in Animal Crossing: New Horizons and the game doesn't really give you much pointers so, thought I'd put together a guide.
So once you've set yourself up a tent and done the same for your new neighbours, you can talk to Tom Nook to see what you should do. He'll ask you to show him some of the local wildlife which can be insects or fish.
To catch fish or insects you can either craft your tools or buy them. Crafting's cheaper of course and you'll need to go shake trees for branches before using the crafting desk next to Tom.
These are fairly much like achievements in modern games. Just keep doing different things such as fishing and catching insects and you can redeem them on your NookPhone. Everyday there will be bonus multipliers where you get 2x or more miles for completing a task.
Nook's Cranny Shop and Building a House
After paying off your first debt using miles, your airfare to the island, you can turn your tent into a small house by taking out 98,000 Bell loan. It doesn't have to paid to get your house building so start that first, then you can go farming goodies for bells. You can then repay it and repeat to expand your house.
Speak to Timmy too so you can get a proper shop built but you'll have to donate materials for it.
Meeting New Residents and Visiting Other Islands
Redeem tickets from the community centre to fly to new islands and invite new villagers (after you've built your own house). You can also open up your port so that friends can visit your island but if you want to do that over the internet, you'll need a Nintendo Online subscription unfortunately.
You can either choose to "Dream" where you can go sleep in your home and visit someone's island without them being online or, you can fly from the airport to hangout.
These are very rare which you can get by hitting a stone with a stone axe (not iron unless you want to destroy it!) or a shovel.
Some people like to dig two holes around them to get the full 8 items but you can also just grow bushes around the stones. Then you must use the shovel because the axe is too short. Make sure you tap away quickly until all 8 spaces are filled around the stone. Otherwise, you can still get fewer than 8.
You can use your Nook Miles to redeem tickets to Mysterious Island to get more as the number of stones are limited daily.
More Tools and Better Tools - Axe, Shovel, Vault Pole
Once you've shown two of each kind of fish and insect Tom will let you craft an axe for you to gather wood. You can use it to hit stones for nuggets and other metallic goods like Bells too! Just don't use the metallic axe unless you're chopping down trees.
Eventually you'll want to redeem the "Pretty Good Tools" recipe from the Nook Stop machine so they don't break so quickly. Keep donating to Nook and you'll be on your way to unlocking the museum too. Unlocking the museum unlocks the shovel for digging fossils and also a vault pole that gives you a cheaper way of crossing the river before you can afford bridges.
And the vault pole doesn't break so you don't have to worry about being stranded.
Quick Change - Tool Ring
At first you can press down on the D-pad to put away tools, left/right to cycle through them. Redeem the Tool Ring using miles will let you press up on the D-pad and make it a bit more organised and quicker.
Fruit for Extra Strength
Eating any kind of fruit increases your food counter which gives you extra strength for digging up trees or smashing rocks to clear some room on your island. You can even dig up trees from Mystery Island and bring them back to your own. Obviously be careful what you destroy such as stones they give you rare nuggets.
Bridges and Ladders
Once you've met and invited 3 neighbours from flights to Mysterious Island you can talk to Tom about building bridges to get to the other parts of the island. Setup the 3 spots for the new homes and he'll also give you a ladder to climb cliffs.
Each new neighbour takes a day to move in (they don't all move in at once), the Resident Services tent will take another day to get upgraded to a town hall which will let you build more bridges and inclines for climbing the cliffs.
Don't sell any of the raw materials including the common apples and weeds. Use them to craft something more valuable and sell that instead. You'll need them for quests too anyway.
Once you've built the Nook's Cranny shop, you can build specific items to sell for double. Bell Vouchers worth 3000 Bells each for 500 Miles become available once you've built the Resident Services tent is upgraded to a full-sized town hall. Just collect the ticket and sell at the new RS building.
Sell What You Don't Need
To start off, you'll want to keep the raw materials you get from harvesting wood and mining, so just go fishing and catching bugs. The rarer they are the more they're worth of course. Just going for big fishes is mostly good enough. Fossils you already have can be sold off.
You can buy the wet suit so that you can go swimming for sea creatures too which are worth even more; probably because it takes a lot more time to swim around.
If you find a scallop while swimming around your island, you'll meet Pascal the otter who will mostly offer you a pearl in exchange which is worth 10,000 bells, same as a gold nugget (but you might want to keep them for crafting).
Anything goes really!
Timmy and Tommy will buy these items of the day for double the Bells but they're really not worth the trouble because of the materials you need and no batch crafting option. However, if it's part of the daily miles you might as well.
You can mine your boulders for nuggets once a day and it seems you can get bags of bells from them daily too. If you're lucky, you might arrive on a Mystery Island full of them.
If you find a glowing spot, there will be a bag of money. Bury some money in the spot and you'll grow a money tree with 3 bags of whatever you buried e.g. 10,000 bells will grow into a tree of 3x bags of 10,000 bells. I think there are reports that you can't get more than 10,000 bells per bag so that's as high as you should bury.
You'll probably see a lot of people asking about turnip prices on Twitter. On Sundays, Daisy comes by to sell turnips between 4am until noon for 90 - 110 bells. You can then sell them on the market when the prices are higher which can range between 15 to 650 each and change twice a day; once before noon and once after.
Prices are even different on other player's islands so you can visit their island to check too. Unfortunately, you can't put them in house storage so you'll need somewhere to dump them which, can bring down your house or island ratings.
Be warned though, they go bad in 1 week so you'll have to sell them before Daisy comes round on Sunday again... So keep checking those prices twice a day. They can suddenly fluctuate in the afternoon e.g. they were 75 bells in the morning then 123 bells in the afternoon. Another time it was 153 in the morning and then 483 in the afternoon so it's really up to you to decide when to sell them off or not. For me when I was playing offline, it was mostly highest midweek on Wednesdays and Thursdays when I checked twice daily.
An online subscription would make it easier if you use sites like Turnip Exchange (Discord account required) where people share their island codes in exchange for goods such as NMTs (Nook Mile Tickets) although, as soon as I got a subscription prices stopped going up.
The only downside visiting stranger's islands is you'll probably be going through a lot of arrival/leaving screens...
Please note there will also be people using hacks and they will label their island as a "mod island". You could end up buying a hacked item that will break your game so beware.
It's worth noting you can make plenty of bells for maxing out your house just by playing daily and selling what you collect or craft from doing the miles tasks so you don't have to risk buying turnips. Being able to grow crops since the v2.0 update makes it even easier as they're worth more than fruits.
And no you can't grow your own by just burying them like other plants.
As a bit of trivia, investment stock and turnips have the same pronunciation in Japanese, "kabu" so it's a bit of word play here, just like "stalk market".
Wasps nests can fall from trees and if you get stung you'll have to use medicine. Get stung a second time without using medicine and you'll pass out then wake up outside your house. You can buy medicine or to craft your own medicine, speak to any resident after you get stung and they'll give you the recipe; weeds and wasps nest.
Wasps aren't hard to catch. Keep your net out, shake trees from the front until one drops then you can hit A to catch them immediately. There are only 3 wasps each day so you can just shake a small group of trees for them before hitting them for wood. Fruit trees never have wasps in them. Once you've caught 3, you know the rest will be safe. Each wasp is worth 2500 bells each while the nests are worth 300 bells too. However, if you wait until Flick the lizard appears you can sell the wasps for 3750 bells each.
For scorpions that appear at night, you need to have your net out, hold A and approach them slowly when their claws are down. Once close enough, release A to net them. Tarantulas are the same but they're a bit harder to spot because they look like the common cricket. They're worth 8000 bells at the shop but obviously Flick will buy them for more at 12,000 bells each if you can wait.
Note: Tarantulas will not attack you unless you're holding a net in your hand.
If you fly to Mystery Island during the night, you just might reach the elusive "Scorpion/Tarantula Island" where you're just surrounded by the poisonous creatures. At which point you'll probably want to dig holes to protect yourself then, just abandon everything in your bag and fill it up ready for Flick's next visit!
Version 2.0 update allows you to cook too and a lot of the ingredients you can't get from the shops. However, special days like Turkey Day will let you trade items with your villagers for some of those ingredients e.g. Turkey Day let me get a hold of pumpkins and potatoes that I could bury to grow.
You can also take a boat trip with Kapp'n which is only available once a day for 1000 miles. If you press B a couple of times when he sings, he'll stop singing and move onto the island more quickly.
Again, having an online subscription so you can just ask on Discord or forums (more on that later) will make things easier.
Don't forget to visit Harv's Island where you can pay 100,000 bells for Leif (and others) to set up shop permanently there so you don't have to wait for him to randomly appear. Another new feature of the version 2.0 update.
Keep fulfilling Tom's quests and you'll eventually have access to the Island Designer app which will allow you to customise your island's landscape.
If you're after certain items or furniture, the best thing to do is have a subscription then visit forums. Or you can signup to Discord and join the Animal Crossing channel there to advertise what you're after as a wishlist using a site such as Nook Exchange.
I got fairly much all the items I wanted from advertising there then exchanging on my own or other player's islands. v2.0 of the game makes getting different variations of furniture you can't obtain by customising easier by "recycling" them on Harv's Island once you help set up the stall.