What product are you making? Will you be the user of the product? What is your familiarity with the industry you are in?
1. Learn about the space:
---- Buy/sign up for all alternative services/products or products that are common
---- What are people saying? Read all the reviews you can for the products.
---- Give the product to people around you and get their feedback
---- Go and talk to your potential users in person / on a call.
2. Summarize the major pain points / value you can add that is not added. These are your hypotheses.
3. Build a proof-of-concept prototype or multiple prototypes to test each hypothesis. Optimize for speed.
4. Interview your users (call them, no email or texts) and summarize. Repeat point 2 and 3.
5. Sign up for all newsletters in your field / follow people on twitter in the same space to keep up to date on what is happening.
People like to talk tools being used but this depends on person. GSheets worked for me for collecting reviews, but large sheets of paper and whiteboard worked for Summarizing/synthesis of learnings. Do what feels the most natural.
Do not optimize for making a robust and flawless system for research - this takes a lot of time to perfect and rather spend time iterating on the product.