Collecting project requirements

I always encounter the problem of collecting requirements before starting a new project. I do this in different programs depending on the complexity of the project, when in Word, when in Mindjet MindManager. I tried to find special software or information, including on the habr — I did not find it, although I look at the topic “Requirements Collection” here often. So, I think this issue will be relevant to Habré.

At the moment I know of several professional products created for structuring, collecting and analyzing requirements:

- Rational RequisitePro
- AllFusion Process Modeler (previously: BPwin)
- AllFusion ERwin Data Modeler (previously: ERwin)
- Doors
- Borland Caliber RM
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How do you collect / structure / analyze project requirements?