The stock answers to this and all other essentially artistic questions, all questions which don't resolve to some immediate technical solution, are:
- Practice, practice, practice!
- Horizontal lines create feelings of... yellow makes people feel... etc
Regular readers will be able to predict accurately that I think these are bunk. Well, not quite bunk, there are germs of truth.
To address the first one, undirected practice is almost completely worthless. Even focused practice, where you shoot and examine your work, is nearly useless. To get places efficiently, one can go quite a bit beyond that. Spending 10,000 hours taking 'properly exposed' photos from eye level will teach you very little.
To address the second, well, these things are all neat ideas, but presenting them as fixed rules is quite harmful. They are not fixed.
The correct answer is directed practice. You want to try things out, specific things. You want to learn what the visual effects actually are of the technical things you can do. What does this cactus look like up close? in B&W? What if you shoot it dark? Bright? In the morning? From far away with a very long lens?
This develops a visual vocabulary. By doing and looking, you learn at a visceral level what is possible, visually. You may learn some trends about horizontal lines and the color yellow along the way, but more usefully you will develop an intimate photographic idea of what it looks like when you do that, or that, or this other thing.
Practice thus, look at lots of other photographs (and maybe some paintings), and you'll develop a deep vocabulary of what is visually possible, together with the technical mastery to employ that vocabulary.
Now look at the thing you're trying to shoot, and think about what you're trying to say, what emotion you're trying to capture. Riffle through your vocabulary "words" of visual effects, and visualize roughly what they look like. You will, with luck, get a couple ideas. It's possible that you'll suddenly see that enhancing the yellow colors will make the place feel cold, and that the horizontal lines will make it feel dynamic. That's not usually how it goes, but maybe it's just what will happen with the rock you're trying to make feel happy.
So, the first one is true, as well as false. Practice, but don't just go poke keys on the piano at random. Learn your scales and chords, and listen to them.
So, the second one is true in a way as well. It's about knowing what diagonal lines, dark shadows, and the color red look like. They're gonna do something, it's up to you to see what they're gonna do.
There's a bunch of exercises over on my Introduction to Photography thing that might help here. They're supposed to.