Researching the domestic laws of a foreign country, or implementation at the national level of international obligations, will be different pretty much every time. Unfortunately, there is no one comprehensive database for searching all the laws of every country, although some resources exist that cover multiple countries for certain jurisdictions, or for certain topics (e.g. tax).
As laid out in the general strategy here, your first steps should be:
If you are having difficulty finding the law, or at any point in the process above, please contact Gabriela Femenia, Biddle's Foreign and International Law Librarian, for help getting what you need!
Before trying to find and read a country's law in a given area, you must understand that country's legal system and, if appropriate, the specific area of law as well. A good introduction to that country and/or area of law will help you understand what the essential sources of law are in that jurisdiction, how they get made, and how they are enforced.
Biddle has legal system overviews and introductions for most countries and subjects, so begin by checking LOLA using terms like "legal system (country)". A few examples of useful books and e-resources are listed here. A good research guide will most likely also point you to useful introductory material on your target country.
German Legal System and Laws by 
The Legal System of the People's Republic of China in a Nutshell by 
Whether you're new to a jurisdiction or just not sure you know the most efficient way to research, a good research guide can save you enormous amounts of time and frustration. A good one will also provide at least some introduction to the jurisdiction as well as pointing you to the right websites, databases, and publications for that country, and some will even give you annotated bibliographies of the best secondary sources to look at.
The links below will point you to some of the best research guides for national law research. If you don't find the information you need here, a judicious Google search for "legal research guide [your country or topic] will often turn up the right guidance.
Additional Sources for Guides
Libraries with big foreign law collections also tend to be good at producing research guides, e.g. Georgetown, Harvard, Columbia and Yale in general, and University of Washington for Japan, Korea and China. Biddle currently has guides on human rights, treaties, and rule of law.
Country-Specific Research Manuals
For some jurisdictions, you may be able to find a detailed legal research manual prepared for researchers or practicing attorneys. This is most likely to be the case for common-law jurisdictions like the United Kingdom or Canada, but some are also available for other countries, e.g. China. Check LOLA to see if one is available for your specific country or topic.