The Seattle-Tacoma International Airport is the best way to reach Seattle. The airport is well connected and you will be able to find regular flights to and from major cities. You will also be able to find bus services from major cities in the US but these are often long journeys that are inconvenient if you have a lot of luggage.
HOW TO GET AROUND SEATTLE
Walk: Walking might get tiresome but is a good option if you combine it with the Metro.
Metro Transit: The Metro networks work really well. The schedules and timings are quite easy to understand.
Bicycle: Bicycles are not a bad way of getting around. You can easily rent one to travel around the cities. The roads are favorable to cycling.
Cars are not recommended for getting around Seattle as it can get pretty crowded during rush hours. It is better to book Seattle tours to explore the city on their own transportation mode.