What is your objective: to include a few numbers in a report (borrow), or to analyze data (repurpose)?
What unit of observation do you want to describe?
Do you need aggregated (summarized) data or raw microdata or spatial data or ...?
What software do you intend (or are you willing) to use?
In what format would you like the data delivered? What format(s) will you settle for?
modified from Jake Carlson at ICPSR, 2012