Brainstorming is a very useful technique for discovering new ideas. I think it should be practiced daily by every designer. It helps to unleash creativity and to give a direction to our mind, so that it stops thinking about unnecessary things.
Sketching ideas on paper is common, but you can also use tools like FreeMind, which help you organize your thoughts visually. If you want to innovate, it becomes increasingly important to have both bright ideas and efficient implementation.