The Texas State Law Library is a good place to start when researching Texas laws. Those in or near Austin can visit it at the Tom C. Clark Building on West 14th Street, and they also maintain a website with many resources, including online chat with librarians.
There are several other good online resources for researching Texas laws. The University of Texas School of Law's Tarlton Law Library maintains a website that has many other resources, including a directory of other websites with information on Texas law. The Library of Congress also maintains a webpage with many links to Texas law resources.