Playing by ear can be a lot of things. For players who start in mid or later life, learning to identify the key can be quite challenging. Some teachers are happy to teach what might be summarised as "basic jamming" as a goal, most aren't.

I have one teacher I've seen over the time I've been playing, who I get on with very well. He started by teaching me basic chords and keeping time, and since then most of our sessions have been in the form of working on particular tunes or forms, or smoothing out the problems in something I've picked up on my travels (I work in the offshore oil industry so my lessons aren't regular). There are some big gaps in what I've learnt but he has kept my motivation going.

I had another teacher a couple of years ago for a few months, working in the South West. His view was that older starters tend to suffer from lack of time, self-consciousness, lack of family support and lack of knowledge of the genre. He felt that if you try and teach a 45-year-old to play Twinkle Little Star, they will not take it in for these reasons. He taught me some basic BG chord progressions and how to anticipate, to some extent, where the music was likely to go, and this was very useful.

However I've also had a couple of teachers - for fairly short periods - who didn't take this view and this didn't work out.

I tend to go to BG sessions, although I'm not a BG player. The reason is simple. It does tend to be something of a cliche, but experience has tended to be that if you go to a BG session and don't really know what is going on, someone will give you a bit of a steer in the right direction, whereas at a traditional session you will be ignored at best. My favourite session is a local group which plays country, traditional and pretty well anything anyone brings in.

Where does this lead? Good question. FWIW, I'd say learn to identify C, D and G reliably and quickly. Learn 4:4, 3:4 and 6:8 times. At that point you will some sort of handle in what is happening and will start to nake some actual progress.