The Witness is a game about rules and making sure you obey these rules to solve puzzles. It can be extremely tricky, frustrating, and at times feel like an impossible task. That's why I've come up with some spoiler-free tips that will hopefully guide you to success while still making it seem like you did all the hard work. Your road to line-drawing glory lies ahead.
New symbols should be introduced with easy puzzles
If the puzzle features symbols you're not familiar with, you most likely haven't found the 'tutorial area' for that symbol type. The game never throws you into the deep end with a puzzle without having offered a series of puzzles that gradually teach you the rules. If this describes your situation, move away and look around for the teaching zone.
Learn the symbol rules and recheck them
If you think you know the rules for all the symbols in the puzzle yet still can't solve it, double check by going back over the panels that taught you. Following this, make sure you're not doing anything stupid, like incorrectly combining blocks into a block of 6 when it should be 8.
What do I do in this location?
Part of the brilliance of The Witness is discovering the secrets. If you're in a new location and you can't really work out what you're meant to do there in order to make progress, see if you can find any clues around you. Are any objects giving you hints? Look all around the puzzle panels and survey the area. Listen to the sounds around you. Pay attention to everything.
Take the game into real life
Get some paper and a pencil and draw out the puzzles if you think it will help. At points I even cut out pieces to rearrange in front of me. Some people find visualising shapes and how they fit together with others a lot easier than others. When you're rotating shapes this can be even harder to picture in your head. If you draw things out it can be a lot easier.
The puzzle seems impossible
It's not impossible. It's probably very tricky, but it's not impossible. See my previous points and my next point.
Don't be afraid to leave a puzzle for later
If you think you have the rules correct in your head and have followed all my other tips, there's no point banging your head against a brick wall for hours. Leave the puzzle alone and come back to it later. On numerous occasions I did this and solved the puzzle within a minute when I returned.