Thorough documentation is vital for understanding your data and making your research reproducible:
Detailed Records: Always note the data source, download date, and any specific terms of use.
Processing Log: Keep a clear, step-by-step record of every change you make to the raw data, including cleaning and recoding.
The Codebook is Key: The original codebook from the data archive is your most important guide. It defines variables, explains missing data, and provides critical methodological details. Never use a data set without studying its codebook.