The latest collection of court-mandated rules for games and games developers have been issued from the Authority. Who is me. And if you want things to go smoothly, you'll follow my instructions. Call the police, and I start killing hostages. So nice and slowly, put down your weapons and obey me. And obey the first fifty rules too.
DO let me skip your game's tutorial. Even if you've, because you're THE WORST PERSON ON EARTH, made your tutorial levels part of the overall game. Every time I read a book, I'm not required to learn the alphabet again from scratch. Every time I ride a bike, I don't have to go through the stabilisers phase again. Playing your game should not require me to "learn" it from the start each time, unless I express a desire to do so. Which in turn means, stop making your tutorial a part of the main game, or I'm going to drop heavy things on your head until you have to learn the alphabet all over again.
DON'T call your game an "adventure" unless it's, well, an adventure. This is a disease that has existed for many years, but the blight is spreading, as everything from platform games to brawlers are being described by developers and publishers as "adventures". You may have what they think is an adventurous time in the game, but it's like describing your visual novel as an FPS. Adventure games are a genre that go back to the very birth of gaming, identified by their being narrative focused tales of verbiage rather than reflexes. From the original text adventures, through their evolving path of text parsing and eventually pointing and clicking, thems adventure games. Every time you label your resource-management tractor sim an "adventure", you make people hate you. You don't want people to hate you.
DO write maybe five more barks for your NPCs. When non-player characters shout the same three lines over and over and over and over and over and over and over in your game, the only impression I can get is that you never played it before release. It seems improbable that you'd not have played your own game, but then at the same time you don't have screwdrivers sticking out of your gored, bleeding ears, so what am I supposed to conclude? You went to the effort to write their three lines, and then you went to the effort to get a passer-by into the recording studio to grunt them out loud, so why not just make it eight, ten, twenty different lines? If it's because you hate humanity so very, very much, may I gently suggest therapy?
DON'T make a platform game where the gimmick is you can shift between two overlapping worlds. If you think you've had an idea, and that idea is that in your platform game you can shift between two overlapping worlds, then you haven't had an idea at all. This is a bit like waking up one day and declaring that you've had the idea to put foodstuffs between two slices of bread. That's someone else's idea. That's the 4th Earl Of Sandwich's idea, and he's going to beat you up. Coincidentally, he was also the first person to think of a platform game where you shift between two overlapping worlds, and he died in 1771.
DO consider the possibility of happy things. It's an odd realisation, that gaming so obsessively focuses either on attempting to recover from negativity or ambivalence. Someone's kidnapped, needs to be avenged, trapped, pursued, dying... How about a game about someone whose day is going really well, and is about to get a whole lot better? Does no one have a positive tale to tell, an optimistic adventure to share? Where's my game about everything going really flipping well?
DON'T release your game on Early Access because you haven't finished having ideas for it yet. Early Access is for games you haven't finished making yet. You need to have had the ideas first. Releasing the framework of a game, and then "listening to customer feedback", is a cynical, artless act, and I will put fish behind all your radiators if you do it. Come up with your bloody brilliant idea first. If you expect me to do it for you, I also expect a salary and a profit share from the game's success.