I am finding more frequently that people ask me for advice on improving their images. George Barr has some essays that I always recommend, Taking Your Photography To The Next Level:
Alan Briot also has some helpful essays.
There is plenty to read there! But for those who are serious about the artistic side of photography, I think they're worthwhile.
I will add only one brief observation of my own. It's easy to develop one's own personal style, and begin to see all your photographic possibilities through it. When you become good at something, if you're anything like me, you often seek to be better and better at it. But your style can obscure as much as it illuminates. It's hard to realize how powerful this effect is when you photograph by yourself. But when you're in a group of photographers, most of whom quite naturally will have a different style to you, the learning you get simply by looking at how others composed an image in the same place you were at is remarkable. You'll often find yourself thinking "why didn't I see that?!" You didn't see it maybe because you were thinking of something else, and they likewise didn't see what you saw. Maybe you were changing your lens at the wrong moment. But perhaps you couldn't see it because you simply weren't seeing it the same as they were. And even if you had the time, you still may not have seen it, because your personal style meant you simply missed it. It's a humbling and invaluable experience.
Here is an example. Here are a couple of my images:
And finally one by my friend, Alieh. I prefer her one!