As the very basic level, I listen to 2 things - the melody line and the bass line. melody line is basically the "tune" of the song. Bass line (in most music, its the bass guitar) will generally determine the chord. From there, you just fill in the notes in between to get the chords.

But to do the above, you'll first need to understand how to play chords (inversion). At the basic, learn the major and minor. Then progress to Major7, 7th and minor 7th. That will generally take care of songs in most genre and would keep most home keyboardist happy. You can google keyboard charts for chords.

With that, you should be able to figure out how to play a song at the most basic level and should be able to play songs using keyboards with chord function.

Also good to find a teacher to guide - especially if you want to learn proper piano playing.

Good luck and don't give up!

Yup, that's what i meant by inversions.

Here's a link to a simple but effective chord chart

Very difficult question... for me, playing by ear came quite naturally as I had some music foundation (i was classically trained btw). Also, playing by ear and composing could be quite different. To me, playing by ear means to be able to replicate a song / music piece by just listening to it. The structure of the song/music is already there and play by ear just teaches you to identify the structure thru listening. Composing is creating the structure. Kinda like the difference between drawing a picture and tracing a picture.

So, when I create a song, I kinda have a chord structure in mind with my melody (i.e. I can hear the song in my head) - it may not necessary be nice, but the structure is there

So, for someone starting out with basic theory, I can understand the difficulty. It's not so much play by ear now but rather music theory as well as you need to understand what chord goes with what note and what chord progressions you can use.

Maybe if you can post up a sample of your melody. I can perhaps give you an example of chord progressions - no guarantees it will sound good tho.... I'm also not sure what the play-by-ear course teaches so you may want to find out from forummer who have done it or talk to the school.

Anyways, don't get too hung up on all the theory and stuff. Some of the most beautiful songs written have a 3 or 4 chord structure only

There are still some play by ear courses out there and some of them have been listed in the postings above. Do check them out - tho it doesn't look cheap . But if you are really serious about learning, then, think of it as an investment for future joy!

Don't be too bothered about the "traditional" music qualification stuff (ABRSM, Trinity) if you do not intend to teach. Just learn to play for self enjoyment. Once you get the hang of it, memorising won't be an issue. It'll come second nature to you after a while