Understand how fabrics move, drape, breathe, react when worn, etc. Your in-depth knowledge of fabric is absolutely essential to using it properly when designing. Also know where to source materials from.
Learn from existing designers, not just who they are, but their backgrounds, their signature style, the learning that they undertook, where they studied. Knowing this will help you to be a better designer yourself, as you can borrow and build on their ideas.
