**You need a visual library**

http://graphicdesign.stackexchange.com/questions/16405/what-is-a-visual-library-and-how-to-work-on-it

Practice like others have said and looking at a lot of design, art, the world really is how you get there.

Composition, Spacing and Color Theory are all parts of this visual library that needs to eventually exist at least in part in your head. All of us have some references, art, inspiration that we keep handy - but that's only to supplement that vast number of images that a designer already knows in their head.

Learning the tools WILL NOT get you there. Take a good book that you like and know really well. Close your eyes and visualize a character or a scene. Look - you just solved a design problem without any photoshop, illustrator, gimp, pen, pencil or anything else. Now you know what it should look like --- now you use the required tools to build it.

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To put it into more of a metaphor let's say you're going to build a wall. Well you know what walls look like so you have a visual library of some options. Now you think okay I want this wall to be this high and because its for this purpose I'll need this material. Let's say you visualize a nice stone mason wall. Only once you're at that point do you think, okay so I'm going to need to learn to dig a trench, and lay mortar, and understand the foundation, and the vertical joints. And to do these things I'm going to need to learn this tool, and that tool.

But see, you didn't need to know any of those tools or techniques to visualize a wall. You visualized that all from your experience with the world.