How can I get good at visual and interaction design?
First things first: it is a mistake to constrain the word "design" to only "making things look pretty". That aspect is actually the least important, in my opinion.
Design is about understanding problems. When you understand a problem fully, the solution nearly always becomes obvious.
The road to becoming a good designer is the same path as becoming good at anything else: practice, practice, practice.
Give yourself design problems, both simple and complex. Think about re-solving things you encounter every day: Stop lights. Cross walk markings. Microwave oven panels. Automated teller machines. Point of sale credit card machines. Paperclips.
All around you are real-world problems that have designed solutions. Study these problems and their solutions. Research why certain decisions were made (why are stop signs red?). Come up with better ones.
Build better mouse traps, as it were.
Pay attention to details, especially with well-designed objects and systems. A great thing to study is the interiors of aircraft. Why are things locked in certain ways? Why are the cabinets sized specifically?
Understand simplicity and ease-of-use. Why do police officers carry their gear in certain ways? What is the value of having the communications nodule mounted on the shoulder? Why are sidearms never slung for cross-draw? Police and military equipment is usually top-notch for simplicity and easy of use (consider explosive charges, stamped with "THIS SIDE TOWARDS ENEMY").
When you start to understand the problems, you understand the solutions. And you can make better ones. And, most importantly, you will be able to communicate your designs.
Practice, practice, practice.
Practice your tools. Learn Photoshop, or Illustrator, or whatever. Learn color theory and psychology.
Learn when to innovate and when to imitate. Be comfortable with stealing ideas and having your own ideas stolen.
Practice, practice, practice.
And then you will be good.
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