Do - Exactly any/everything someone says or asks you to do.
There are rare instances where the player is told to do something that must be done in order for the game to progress, but, there will be no map icon, quest marker, or reminder dialog for the action.

Don’t - Remove / Hammer tilled soil found outside of town.
This is deliberately vague so as not to be a spoiler.

Don’t - Remove / Hammer conspicuous blocks around mini medal puzzle locations.
This is deliberately vague so as not to be a spoiler.

Don’t - Plant any crop type before you are asked or told to by an NPC.
You may be able to beforehand, and, nothing goes "wrong" if you do,
but sometimes it can be confusing when an NPC asks you to plant a crop,
they actually need to be planted, and also sprout and / or grow to move things forward.
Even if you have the crop type already planted and grown,
or even harvested, the NPC may not react and move dialog forward.

Don’t - Build any building outside the town’s predefined limits.
NPC AIs will not correctly interact with buildings outside town limits.
(You can see my picture guide for town limits HERE.)

Don’t - Build anything closer than ~10 tiles away from the town bell or center square.
While nothing goes “wrong” if a player does, all kinds of broken camera angles and NPC positioning occurs if you do. This is because many cut scenes are centered around those locations, and NPCs will end up bizarrely on top of buildings,
and the camera can end up behind a wall or pointing at a roof.

At this point I have played deep into the 3rd island.
I have not updated this guide with specifics per island because by following some "Golden Rules" I discovered in the 1st island, I've avoided any other issues.

In general, the "Golden Rules" are...

• Do - Exactly any/everything someone says or asks you to do,
  as soon as you can after they tell you to do it,
  and avoiding doing anything else before you do it first.
  
  
• Do - Talk to the NPC that gave you a quest after you finish it even if they already spoke to you.
  
  
• Don’t - Remove / Hammer conspicuous / unique blocks when encountered for the 1st time
  until the game / a NPC leads you to do so.
  
  
• Don’t - Tear down original structures in towns.
  
  
• Don’t - "Work Ahead" on anything you find a way to do before the game prompts you.
  
  
• Don’t - Touch secret or hidden areas you find before the game leads you to it.
  (Builders Puzzles are an exception.)
  
  
• Don’t - Build any building outside the town’s predefined limits.
  If you want to build items "for fun" make them very far away from town.
  (You can see my picture guide for town limits HERE.)

Understand that not following thees guidelines in most cases will not "break" the game.
However, it can help to avoid significant aggravation, confusion or complications to quest objectives.

• Special Note - There is a specific series of map pins you are expected to travel for a mission on the 3rd island, and each lead to a non-violent talking monster.
  Be sure to walk along the ground on the most obvious route.
  Do not use the wind cape to "shortcut".
  This is deliberately vague so as not to be a spoiler.