In my cruise thread, someone was talking about how they were going to negotiate renting a car at the airport, with returning it on their last day and getting back to the pier. I posted my advice there and wanted to share it here:
FOR PEOPLE RENTING A CAR IN SEATTLE--ADVICE FROM A LIFETIME SEATTLITE:
I would personally recommend renting a car** downtown if you can, rather than at the airport. The airport is 30+ minutes away from downtown (depending on traffic), and it isn't super practical to be downtown at your hotel, then drive back south to the airport to drop off your car, then take a shuttle back to the ship--embarkation day being the one day you are probably on the tightest schedule, with packing, checking out, wrangling bags (then returning a car, re-wrangling bags, taking a shuttle, re-wrangling bags at the terminal, etc). I would recommend you take a shuttle (your hotel may offer a free one) or the light rail or a taxi into downtown from the airport, then get your car rental downtown. That way your return is downtown as well.
Enterprise rentals will pick you up and drop you off within a reasonable radius, so you could return your car downtown and then they can drive you to the pier. I am sure other rental companies have their own shuttles and versions of this service they can offer. (**That is, if you need a rental car at all! See ** below)
I will also mention that parking downtown is a bear, and our streets are seriously messed up--one way streets all over the place, we are NOT a clear grid because of the many hills so some roads and intersections are really confusing, insanely steep inclines, bad drivers and bad traffic

...SEATTLITES often remark what a PITA it is to navigate in Seattle and some refuse to drive down there at all. So I imagine it is only worse for visitors!
**Ultimately, you may not NEED a car. Seattle has SO MUCH to offer in a small area--the city really isn't that large, but it is packed with awesomeness. Hubby and I recently did a "staycation-esque" trip where we spent a long weekend in a hotel downtown (this is about 10 minutes from our home). We parked our car in the hotel garage for the entire time and
~ went to a show at the 5th Avenue (there are also multiple movie theaters and even some indie live theater places in the area--see a concert at the Paramount, or a rare Cinemascope show at the Cinerama, or an IMAX or IMAX 3D show at the Seattle Center)
~ took a food tour at the market (Pike Place Market really is awesome, even to us locals)
~ went out to dinner at some restaurants we had always wanted to try (Dear foodies, Go to Purple. Just go. You're welcome.)
~ went shopping at boutiques (and the Nordstrom flagship store, which we love)
~ went to the Seattle Center (we adore the Science Center--a must see if you're geeks like us

~ spent an afternoon on the waterfront, where you could
~~do more shopping
~~eat more great food and/or:
~~ go to the aquarium
~~take a harbor tour (if you desire more boat time in your life)Duck tour, There is also:
~ the Underground Seattle tour (another one I always highly recommend)
~ go to the Seattle Art Museum
~ go to the EMP/Science Fiction Museum
~ ride the monorail
~ hit the arcade at Gameworks
If you're more outdoorsy:
~ rent a bike and bike the Ship Canal Trail
http://www.yelp.com/biz/the-bicycle-repair-shop-seattle
~ visit the Olympic Sculpture Park
~ take a bus to Lake Union, ride the S.L.U.T. then rent a kayak and go out on the lake
...the list goes on.
And ALL of it does not require a car in the least, and a car may in fact hinder your transportation and take up valuable time with navigating the roads, finding parking, etc. A car really is a needless expense unless you have plans further away.
A good rule of thumb: if the Google Map directions from your hotel to your intended activity/destination indicate that you will be getting on I-5 for more than 3-5 miles, or include any time on 520 or I-90, then a car is for you. Otherwise, I say pass it up.
And if you need any further advice or ideas from a local, I am....wait for it...ALL EARS!
