When you use a secondary source, you not only find case law and statutes, but also vocabulary that can improve your searches. To further improve your searches see the glossary of legal terms within this guide.
Good places to start your Washington state legal research
Compilation of all permanent laws now in force. It is a collection of Session Laws (enacted by the Legislature, and signed by the Governor, or enacted via the initiative process), arranged by topic, with amendments added and repealed laws removed.
The Code Reviser codifies, revises, corrects and publishes the state laws and regulations. From here you can link to the statutes, the Revised Code of Washington (RCW); and regulations, the Washington Administrative Code, (WAC).