Seattle is a walkable city in its core neighbourhoods — downtown, Capitol Hill, Pike Place, Pioneer Square, and the waterfront are all within comfortable walking distance of each other — but the hills are steep and the city sprawls in all directions. For anything beyond the central core, public transit is the sensible option.
Light rail: Sound Transit's Link Light Rail now extends from Sea-Tac Airport through downtown and north to the University District and beyond. The line is fast, frequent (every 8–15 minutes), and covers the most tourist-relevant stops. A single-trip fare is around $2.50–$3.50 depending on distance. ORCA cards (reloadable smart cards) can be purchased at any station.
Bus: King County Metro buses cover the entire city with reasonable frequency. The Rapid Ride lines (A through H) run more frequently on major corridors. The ORCA card works on all transit. Downtown Seattle has a free-ride zone on some routes, though this has been reduced over the years — check current details.
Ferries: Washington State Ferries are part of the regional transit system and are genuinely useful. The Bainbridge Island ferry departs from Colman Dock (Pier 52) at the foot of Marion Street and gives you a 35-minute crossing of Puget Sound with excellent views of the Seattle skyline. This is one of the best cheap excursions from the city — you don't need to leave the boat. Ferries also run to Bremerton and other Puget Sound destinations.
Driving: Parking downtown is expensive and street parking is metered and competitive. The city's hills and one-way streets are confusing. Seattle traffic is consistently rated among the worst in the United States. Drive only if you are going somewhere the transit doesn't reach.
Cycling: Seattle has a growing network of protected bike lanes, and the Burke-Gilman Trail is a paved multi-use path running from Ballard through the University District to Kirkland, largely traffic-free. Bike share (Lime, Jump) is available throughout the central neighbourhoods.