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Learn anything you can related to photography then apply everything that you've learn every time you shoot.

These would be the very basic you should learn first:

-White balance. (how to use it correctly or creatively).

-Shutter speed. (what speed do you need for specific effect)

-Aperture. (do you need a small depth of field (DOF) or you need plenty)

-Iso. (do you need to crank it up to get a faster shutter speed?)

-Exposure Values. (give you a full understanding of how the exposure work)

-Exposure triangle. (give you a full understanding of how to get the correct exposure)

-Rule of thirds. (help you improve your composition skills)

-How to critic a photo to better auto critic your own work.

-More on composition.

-Understand natural light.

Then you should learn about the type of photography you would like to get better at it.

-Portraiture.

-Action, sport.

-Wildlife.

-Macro.

-Street photography.

-Landscape.

-Long exposure.

-Automobile, racing.

-Aerial photography.

-Architecture.

-Concert photography.

-Food photography.

-Wedding

-etc.

Then you should learn about materials.

-Compact, bridge camera.

-Evil camera or hybride camera.

-Dslr.

-Type of lens and what they are best use for.

-Flash photography.

-Light modifier (reflector, umbrella, soft box etc.)

-Etc.

You can find allot of info by searching with Google, buying books or join your local photography club if you have one.

Taking professional photos do not require you to be a professional, all you need is the knowledge & the right tools to get things done, when someone reach this level the only difference from him/her and a professional will be money, one will get paid while the other doesn't get paid.

By learning photography like a pro does.