I teach piano by ear and in all those years I've taught hundreds of people how to play the piano by ear. But playing the piano by ear doesn't mean playing the piano by magic!
It can be fun, it can be liberating, it can even be magical but it will take some hard work and a very good amount of discipline.
But there are some things you can do to make the hard work not so hard.
So, here are 5 must do's that will help improving the quality of your learning process and if you have the necessary discipline, the results will come a lot easier and permanently.
1. Use a metronome (or a drum beat)
Always learn and practice using a metronome. You don't have to play a song using a metronome once you master it - I never play songs using a metronome (except some rare occasions). But I always learn and practice songs using a metronome and so should you. It keeps you honest. Varying the tempo of a song should be a feature intentionally added to your performance, not a handicap.
It's almost a complete waste of time to learn or practice a song if your heart and your mind are not there. If you like to play the piano to blow off some steam, to release some tension, to kill time, to get your head out of problems for a few moments...do it. Just don't learn or practice songs while you are in that state. Play whatever you like, improvise, explore the keyboard and try creating some new sounds, anything other than learning and practicing songs. Leave that for when you get yourself in a better headspace so you are able to focus.
3. Play slowly - The slower you practice the faster you learn.
The golden rule is: You have to play the entire song at a speed that will allow you to play the hardest part of the song without stopping, without making mistakes and without breaking the natural flow of the song (and you should use the metronome to do so). It doesn't matter how slow it needs to be.
It's just like watching a movie in slow motion. Nothing in the movie changes just because it's been played 4 times slower than the normal speed. And the same applies to the song you're learning. It should sound like a slow motion version of the song. Once you have mastered playing the song in the slowest tempo, use the metronome and speed up to a new tempo. The new tempo will be determined by the same rule - you need to be able to play the hardest part of the song without stopping, slowing down or making mistakes. Follow this process until you can play the song a little bit faster than the desired tempo. You will be playing brilliantly once you go back to the desired tempo.
4. Don't perfect the mistake
If you make a mistake, fix it immediately. And once you fix it, repeat the bit in the right way for a few times before moving forward. Never, never, never ignore the mistake thinking "I'll come back to it later (because I'm having fun playing the parts I know well)". The more you ignore the mistake the harder it will be to fix it later. And I mean really, really, really hard. Some people never manage to fix it once the mistake is embedded in their muscle memory and worse than that, some people stop noticing the mistake.
5. Have Fun.
There's a balance between practice and fun. One might think that the only outcome to practicing a lot is getting really good at it - which is true. But there's an almost perverse side of practicing a lot. You can lose sight of what playing (and learning) the piano should be about. Playing the piano is supposed to bring joy to yours and other people's lives. So keep an eye on the pain/gain ratio and find your won point of balance.
Let me know if one or all these tips were in any way helpful to you.
Also, please let me know if you have any other tips or suggestions that had worked well for you in the past.