How to conduct research in a law library?
It depends upon what you're looking for.
laws libraries vary, there's usually law libraries on site at the courthouses, these will contain full volumes of statutory law, my local county law library has the entire volumes of the RCW, the WAC, and United States Code, they also have the minutes of all legislature sessions, the county code, the codes of all cities in the county, rules of evidence etc.
Also some law libraries (mostly at universities) will contain monographs, which are detailed research on a specific subject.
really there's alot of stuff, what are you looking to learn? I may be able to give you more specific advice,
also all of the courthouse law libraries in my area usually have librarians who can help you find what you're looking for.