Principles of Graphic Design

[Koiyuki]

I'm seeking to start a business around selling my graphic design services and works, and to better prepare myself I'm studying some of the online resources teaching things like repetition, harmony and the rule of 3, among others. What principles do you, as either amateur or professional graphic artists, do you think should be learned before anything else?  

[Sonkurra-Taichou]

I was always taught these 7.

Unity
Harmony
Balance
Proportion
Rhythm
Pattern
Movement  

[__oh bella]

I was taught 4 main principals:
Contrast
Repetition.
Alignment.
Proximity.
And just being aware of these totally changed my designs for the better, even in my first week of school!
Also I think balance is very important as well as defining what the purpose of your design is, so you can execute it properly.