My approach to learning new songs have always been a little upside down. I pick a song I want to learn and start by writing down the chords I hear to get familiar with the key and the tune before I work on any improvising. Then here comes the weird part. To find the color chords I listen carefully to the music and find the fingering that I hear. Then, I go through my chord books to find out what the chord is so I can write it down and continue on with my chord mapping. I was blessed with growing up in a family that played many instruments and sang harmony completely by ear. Our mother taught my three siblings and me four part harmony in the age range from 3 to 5 years old.
I'm interested in learning any techniques the guitar players in this forum might incorporate to the process of learning new songs by ear. One more thing that has helped me is what I learned from a teacher in Woodstock, NY named Jamie Andreas. She taught me the importance of 'intentional attention'. Please, don't advise me to learn music theory. I know enough theory to suit my needs but I primarily use the above method. Now if I could only lock away the memory requirements for the recall of the songs I've learned.