A great answer by Brandon Harris to the question posted on Quora:

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.

Rather good advice. Malcolm Gladwell’s 10 000 hour rule (Outliers) comes to mind. The other responses in the thread are similarly good.