Finding the most up-to-date data is often a simply a matter of finding which government or not-for-profit organization collects that data. The internet is generally the best resource for finding these. Most laws and public policies can be found online as well.
To understand policy or the need for it, you will sometimes need other types of data, such as demographics or economic information. These are reliable resources for that type of information.
Find this kind of information online by searching for what you hope to find along with the phrase site:.gov
If you have an idea of which organization puts out the data, you can also search Google for information within that organization by adding site:ahrq.gov (for example).