Interview people who have an involvement in or knowledge of the issue. We often don't take the time to actively find information from live sources. It takes time, effort, and knowledge to get good results, but when done intelligently, the results yield power and often show critical blockages or barriers as well as clear pathways. This is an area that student's seldom use. Don't fear asking questions of experts via email.
Most people willingly share their passions.
Target audience - who's going to use or consume the product or service. My personal favorites involve brainstorming, definitely see synectics . Keeping an open mind and uncovering connections where ever they may exist. Several tools that aid this process reside below. Graphic organizers - a comprehensive index of tools that help analyze, brainstorm, compare and contrast, evaluate, hypothesize, visualize, as well as show interactions and sequences.