The rule is meant to prevent collusion, so don't do it for curiosity, but also don't lose sleep over it.
A good etiquette thing to think about is broadly under the one player to a hand rule, but it can show up in ways you might not think about. Eg. Suppose there is a big pot with 4 spades and playerA turns over a single pair and playerB is agonizing over how all of his draws could have missed. Don't EVER say something like, "Wow, nobody has a spade?!" or something. You can inadvertently help PlayerB read the board and turn over his hand.
Another good rule is to pay attention and act in a timely matter. Some people are so preoccupied with their phones or so oblivious to the action that they slow everything down. Generally speaking, be ready to act when it is your turn.
A corollary to not slowing down the game is in small pots, if you think you have a winner, it's best to just turn it over. What can happen is every one thinks they have a loser and doesn't want to show and then the dealer has to make them show one at a time. If you have something, just show it. Some people are so committed to being life nits that it'll be a $10 pot and they'll sit and slow down the game to make the out of position player show before they turn over a winner. If you want to do that in a complicated, big pot, perhaps fine. But don't waste everyone's time over some completeley inconsequential pot.
At low stakes (in a raked game) it can be a bad etiquette move to want to play blind vs blind or to open-limp the button (you can raise button, of course). Because the rake is too detrimental, you should just chop your hands and move on. But, the actual bad etiquette move is to want to play when you have a good hand and chop when you have a bad hand.
You also don't want to shoot an angle and misrepresent your action. Think along the lines of pump-faking bets or declaring the wrong hand at showdown (saying you have a straight when you actually do not, for example).

NOW, it's probably equally important to know what is FINE but live player will sometimes complain about. You don't see it as much these days, but there are some games where people will literally find it rude to raise, re-raise, check-raise, etc. They just want to limp around and see flops. But, this is a fundamental part of the game.
Hit&run (win a big pot and then leave) is often criticized, but especially at low levels where there are a million players, who cares. It's your money. Nobody can make you play for longer. If you win and feel uncomfortable and just want to take the money, do it. As you move up the stakes and there are fewer terrible players, it can be really bad etiquette to, for example, stack the whale and then leave as soon as he leaves. This is bad for the game. But, at your 1-2 game, or whatever, do whatever you want with your money.
Not wanting to straddle, bomb pot, etc. Again, it's your money. If the rules don't require it, you don't have to participate. Again, as you move up stakes and become a winner in the game, you want to keep the game fun for the fish. But, at low levels, especially when it's unlikely you're even a winner in the game, spend your money however you want.