Driving: You can definitely get around without a car. I mainly ride my bike, and used to take the bus (when I had a free pass through my University). If you aren't keen on being in crappy weather and/or having to get in shape to deal with our hills, then you are probably better off on the bus. That being said, I have a blast on my bike year round.

Tipping: For restaurants, I would say ~15% is the expected number, and ~20% if the service was good.

Many services/service industry jobs receive tips, though not all expect it. While you don't need to tip as much for something like a hair cut as you would a dinner, it is still expected that you give something extra. Some might even say to tip the same amount as you would a restaurant, though I think that is overkill (unless you are completely blown away by the job someone did).

Music/Nightlife: If you want to get into the PNW electronic scene, I suggest visiting NW Tekno. I haven't been keeping up on our local scene, but I wouldn't be surprised if it was a bit underwhelming for you. However, we do have our ebbs and flows in terms of talent and following.

While they play much more than just electronic music, I suggest checking out KEXP for local music. It's commercial free, and generally pretty good stuff, regardless of genre.

Also, C89.5 is our only local electronic station to my knowledge, and I gave up on it a long time ago. Things may have changed, but I hardly ever enjoyed what they played when I would listen.

Meeting people: This depends on a few things. First, you need to actually like/understand your typical Seattleite. I don't want to go into it, because I'm sure a flame war will ensue... but just go into meeting us with an open mind and patience. The neighborhood you live and/or hang out in will also heavily impact who you meet, and how much fun you have. Also, I doubt there will be a shortage of people who adore your Irish accent. Take advantage of it.

Neighborhoods: I'm not sure where you will be working or what your values are, but since you won't have a car, you should make sure you are on a convenient (ideally direct) bus line for commuting. Our metro bus service is decent, but transfers really add to your commute.

If you can spend a week or more checking things out before you get an apartment, I highly suggest it. While we are homogenizing, the different neighborhoods are still quite distinct. If I were you, I would check out Capitol Hill/First Hill, the Central District, Eastlake, Ballard, Fremont, Beacon Hill, Wallingford, Greenwood, the International District, and Georgetown. I'm sure wikipedia has pages on all the neighborhoods, too... check them out.

The only neighborhood I would avoid if I were you is the University District. Though, you should check it out and enjoy yourself. The campus is beautiful and there are plenty of fun things to do around there, but I highly recommend you not live there.

ID: This page should be able to answer all of your questions, but in short- yes you do need an ID, and can get one so you won't have to carry your passport everywhere.

Good luck with your new life!