You can filter the methods based on the problem spaces you are interested in.
Opportunity Canvas
Determine new opportunities & possibilities for existing products
Fishbone Diagram
Visualize the source and cause of problems
5 Whys
Identifying the root cause of a problem
Prioritization Matrix (Urgent Important Matrix / MoSCoW)
Create insight and prioritize tasks or ideas based upon urgency and importance
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COCD Box (How Now Wow Matrix)
Organize brainstorming ideas based on originality and feasibility.
Service Blueprint
Boost and improve service experiences
In-depth interview (user interview)
Gathering accurate qualitative information through one-on-one conversations