By Rail
Sound Transit (http://www.soundtransit.org/) Link Light Rail service connects Sea-Tac Airport, Tukwila and Seattle.
Sounder commuter rail service, operating weekday rush hours only, connects Seattle to Tacoma via Kent and Tukwila.
By bus
Metro Transit electric or diesel city buses actually works pretty well. The web trip planner (http://tripplanner.metrok...) is straightforward and accurate, as long as your bus is on time.
Buses in downtown Seattle are free between 6AM and 7PM in the downtown core of Seattle. Just get on and get off. To read the details refer to Metro Free Bus info (http://transit.metrokc.go...).
Sound Transit diesel and hybrid buses, trains is more expensive, but has many convenient express routes (http://www.soundtransit.o...) that travel South to Tacoma, East Redmond, Bellevue, and North Bothell, Lynnwood. Unlike Metro, it serves the adjoining counties as well.
Outside of the immediate Seattle-Bellevue area, many routes operate only during weekday rush hours. Check your schedules in advance, and beware of holiday service cutbacks. The number of the route also tells you which area of the county it serves:
Below 100
Seattle only100s
South King County200s
Eastside300s
North King County500s
All Sound Transit routes
By car
All but essential for reaching the outermost suburbs and mountains. In addition to the interstates, major routes include SR-520, linking Seattle's University District to Bellevue and Redmond; SR-18, a major freeway in the south county from Federal Way to Issaquah; and SR-509, the alternate route from the airport to Burien and Seattle.
Traffic congestion is a major problem in the Puget Sound area on all freeways and major roads. Avoid traveling during rush hour if you can, particularly along I-5 and across the Lake Washington bridges.