Breaking up your research question into parts to isolate the data you will need to find/gather.
Some things to consider-
Location (US or international? neighborhood or full country?)
Time scale (time series or a single point in time? date range?)
Indicators (what measurable things could help you understand your question)
Would this data exist in this form? Brainstorm people who may have gathered or used this data already to see if you can follow their trail. Some major datasets are listed within this guide, but you may find many more by looking through the literature.
Some data, especially data about sensitive topics, will be difficult to find. You may be able to gather data yourself, or access it through something like a FOIA request, but this will add significant amounts of time to your project. If you need help thinking through the feasibility of your data question, contact a librarian.
Once you've found a dataset, consider:
Point of View- How might the aims of the researcher or organization who initially gathered (or sponsored the gathering of) the data affect the resulting dataset?
Methodology- Do you see obvious limitations in the data posed by the methodology, such as a non-representative sample?
Relevance- Will this dataset actually help you answer your question, or is it a forced fit?
Permissions- Is there clear language giving you rights to reuse this data in your own scholarship?
Recency- Is this the most recent version of the data?
Quality control- Is there an entity responsible for checking the data entry for mistakes?
What's missing?- Would additional data from another source complement your analysis?