When I was a Rule 9 intern at UW Student Legal Services, my favorite thing in the world was to go after sleazy landlords. Many landlords and rental agencies do some pretty terrible things because they can get away with it. Tenants often don't know their rights. Even if they do, it's ordinarily not worth it to pay a lawyer $200/hr to get a $500 deposit back.
The good news is, knowledge is power, and the internet is knowledge. Below are some resources to learn about the Residential Landlord-Tenant Act (RLTA) and what you can do to protect your money.
RLTA: The Act itself. As statutes go, it's pretty easy to grasp.
WSBA: This is a WSBA "pamphlet" on landlord-tenant rights.
Washington Law Help: Find pro bono services.
Housing Justice Project of King County: Pro bono help from volunteers.
UW Student Legal Services: Inexpensive and attentive representation if you are a UW Seattle Campus Student.
A good pamphlet: Explanation of tenants' rights.
If you need guidance, I'm happy to talk to you. Did I mention I love going after sleazy landlords?