What requirements gathering methods do you know and have you applied?

Methods of requirements gathering that I used:

• Interviews — personal conversations with clients and users to identify their needs.
• Questionnaires and surveys — collecting information from a large group of users.
• Document analysis — studying existing documentation, regulations, technical specifications.
• Observation — studying current business processes and user behavior.
• Work meetings and workshops — joint discussion of requirements with stakeholders.
• Prototyping — creating mockups to clarify and agree on requirements.

Each method is chosen depending on the project and available resources.