There are a lot of things you can and should do when you are learning to play the piano, but there is also a list of things that you should never do. These items that I mention are by no means exhaustive, they are just some random items that are worthwhile keeping in mind.
The first thing I’d like to mention is that you should never cross your fingers over each other to play higher or lower notes. The only fingers that should be used to cross over is any finger crossing over your thumb. This not only looks better but it is so much more comfortable to play.
This next one is not actually a never, but it is a hardly ever and that is you should avoid using your thumb on a black note, unless you are playing octaves, or that there is no other reasonable option. Sometimes, it does become necessary, but most of the time you should avoid using your thumb to play a black note.
Another ‘something that you should never do’ is to try and play the piano with your wrists lowered so far that they end up resting on the bit in front of the keyboard part of the piano. There are no circumstances where this is necessary, and if you are doing this, you are making it much harder to press the notes down. Your fingers and wrists may get stiff and sore over time if you have your wrists leaning on the front bit of the piano keyboard. It is so much more comfortable to have your wrists up and your fingers curved and it is protecting your hands and wrists from injury.
The last point I would like to make is that you should never play something on the piano in a way that is going to cause pain in your hands. Sometimes certain stretches between notes can be uncomfortable until you get used to them, but you should never actually be in pain. For this reason I never play a glissando, which is sliding your fingers up or down the notes – it just causes too much pain in my hands.
There is not a whole lot of things that you should never do playing the piano, but there are just a few that make a lot of sense if you think about it.