Lazy, generic listening is what the general public do. Weaker musicians listen to what they like and write off anything that isn’t to their taste. Better players listen with open ears, analytical minds and will see merits in most things, even if they themselves don’t like the music.
Think about the following as you listen. They will inform your choices on what you like and what you don’t like.
How does the line move? Stepwise or jumps and leaps? How long are phrases? Is it smooth and fluid? Jerky? Disjointed?
As you listen try to work out what the underlying harmony is. For a lot of recent pop this is straightforward consisting as it does of three or four chords. Listen to some more advanced or free jazz and this becomes quite challenging!
What is the style of the music? Which elements of the music define the style? Also listen to the performer. Are they playing in an appropriate style? Thrash metal is not the way to play Mozart . . . . or is it?
Listen not only for individual dynamic changes but also for an overall impression of the dynamic level. Much pop for example tends to have dynamic focus on the chorus of songs. Also pay attention to graduation of dynamics. Are changes smooth? Sudden? Appropriate?
If you are listening to more than one player are they playing well together. Is their time well matched? How about tuning? Do they play in a similar style. For good ensembles these details should be virtually indistinguishable.
Between parts and notes this should be appropriate. Perfect tuning is not always the aim of the performer. However if it is, it should be good.
Bass parts can be fundamental to many styles of music. Place some focus on this when you listen. Which instruments, what notes and how does it complement the rest of the parts?
Describe the tone quality of the instruments or voices you can hear.
How do notes start and end? Sharply, smoothly, gradually? If there is more than one performer do they match or are they contrasting?
There are many rhythmic elements you should listen for. Underlying pulse, rate of harmonic change, melodic rhythm and accompaniment are just a few.