Learn from Life
Plein Air painting is for me a great way to learn from life and have fun painting with friends. My most pressing concerns are most of the time getting a quick and clear read, as well as capturing light and mood as I experience them.
There is definitely something magical and irreplaceable about painting the real thing that cannot be replicated by looking at reference. Whenever I have to use photos I always try to imagine how light would have behaved in real life and then I try to capture that feeling.