1. Question: ask the unanswered (and challenging questions) that people ignore
2. Observe: watch your users from a natural and unobtrusive perspective; ethnographic research is best, but you should at least understand how your consumers are using your products/services. How do they want to use products (what are workarounds) and what are they doing that you don't expect?
3. Network: want to spark new ideas? Talk to people from areas outside your traditional circles. Different life experiences and perspectives will force innovation - remember, some of the greatest product innovations stem from uniting two disparate concepts.
4. Experiment: construct hands-on experiences (prototypes!) that provoke unconventional and natural responses from users and allow you to gain new insights. What makes sense on paper may create unexpected behaviors from consumers. Try developing a mock-up and see how your users actually utilize your products. You may be surprised by their response.
5. Associate: draw disparate connections between questions/problems and ideas from seemingly unrelated fields. This is innovation 101.