Take a look at
www.packing.org for good links and details.
Generally speaking, Washington state has pretty good gun laws. The biggest 'bad' law in the state is that no Class Three firearms are allowed; that means no full-auto guns even if you have a federal stamp.
State pre-emption prevents cities or counties from passing more restrictive laws than the state has.
No gun registration is required.
Background checks for handguns purchased through an FFL are waived if you have a Concealed Pistol License.
CPL is shall-issue, no training required, costs around $60 in total fees, and lasts for five years. Prohibited places are public schools, the 21-or-over areas of places that serve liquor, federal buildings, and "outdoor music festivals" (ala Woodstock, I guess).
There's no safe storage requirement, though one nearly passed this last session.
Open carry is a grey area. Carry of a pistol or other deadly weapon is prohibited at a place and time, or under circumstances, or in a manner that either manifests intent to intimidate another, or that warrants alarm for the safety of others. Fuzzy enough that if you open carry in a city, you are likely to alarm someone and be found in violation. But open carry out of town is less problematic, and there are specific exceptions to make it undeniably legal to carry in the woods except during hunting season.
There is no duty to retreat inside your own home, and the 'castle doctrine' allows homeowners to presume that intruders are armed and to respond accordingly.
pax