The musical youths were never in Meiji Shrine: it's a shrine, not a park. They're next door in Yoyogi Park, and on the wide path from there towards Shibuya past the NHK complex. They were previously on Omotesando (the street leading up to Meiji Shrine) when it was closed to traffic on Sundays. Currently, the local goths hang out on the railway bridge to the entrance of Meiji Shrine on Sundays.
If you're in the Park Hyatt: get a taste of electronics in Shinjuku, area between you and the station. Department stores on the other side. Red light district on the other side, to the left. The Park Hyatt, Century Hyatt, Hilton and others in that area are a 7 minute hike into the electronics part of Shinjuku. There's a Keio there which is also very good and can be way cheaper. My friends like the Century Southern Tower because you step out of the elevator into Shinjuku. Rooms are a little small.
Shinjuku = world's busiest railway station. Tokyo = world's largest railway station. Shibuya = world's busiest pedestrian crossing. Ritz Carlton in Roppongi Midtown Project opens in 2 days, so if you've got Park Hyatt-type money that's also worth a look. There's a boutique hotel in Shiodome which some people like hugely.
Yasukuni: yes, strange strange place. Museum is, well, strange. Never seen a shrine museum with a steam train & submarine before.
If you like shrines and temples, look for any sign that seems to have a gothic "Ep" written on it. They'll sell you a book for about 800 yen, and bang some calligraphy in it for another 300 yen. Take that to other shrines/temples and you end up with a momento most people don't know is possible.
Take time to walk down side streets: they get quiet very quickly. Tokyo is like a huge collection of villages. The area around each station is different.
Akihabara: best on Sundays when the main road is closed.
Roppongi: the foreigner's bar & club ghetto. If it rocks your boat, it's fun. If not, you've missed nothing.
Beware of duty free shops: "duty" is 5%. Other shops do deeper discounts. Research beforehand, so you understand which products have universal power supplies and multiple language menus, and which products are 100V and specific to Japan. The main thing about Japan is not that it's cheap, but that everything's on show and can be handled. For live pricing on electronics, check out
www.kakaku.com.
Re Dubliners: among many others, there's a Belgian bar, too: 150 beers available. Dubliners is, I think, owned by Sapporo so it's Guinness and Kilkenny. There are many other bars that sell local and other brands: my local has Yona Yona (a pale ale with a bit of bite) and Spitfire, for example.
From the airport, limousine buses are great because they get you to your hotel. The trains are great because you know how long the journey will take. Apart from one or two obvious places, it's an extraordinarily safe place to wander around, especially as a big foreigner.
If you're with family, Tokyo Disneyland and Disneysea are about 15 minutes out of town.
Buses shut down around 10 pm. Trains shut down around 00:15 -00:45. Taxis are plentiful, clean, automatic doors (so don't touch the door) and way cheaper than London taxis.
If you get to Shinjuku Gyoen (big park), there are two tea houses there where you can get Japanese tea prepared and served by kimono-clad ladies for only 800 yen. Bargain. You can also do it at Hamarikyu (near Shiodome) in a tea house on the tidal pond.
Asakusa Kannon (the "famous" shrine) is a bit of a dump compared to other stuff in the area, but it's the thing to visit as a tourist. There's a long street near there that sells all the plastic display food you'll see outside restaurants.
I dunno, a lot of things to do.