LEARN AS YOU GO.
Before you decide exactly which numbers you need, learn about your topic.
Start wherever you want. (Wikipedia, Google, etc. )
Then, move on to:
From every source, look for:
- Terms -- how are the issues described? What words are used?
- Laws -- what kinds of legislation govern this question?
- Interested parties -- in whose interest is it to collect this information? in whose interest is keeping it a secret?
- Sources -- where did they get their information, can you get that same info?
- Government Sources
- IGO's and NGO's
- Industry Publications
- Standards and Technical Info
- Academic and other Research Institutions
