Hi... this post was made based on my experience as an Arashi fan who does not have a fan club membership.
Most of you may be suprised when looking Arashi ticket price at
http://www.ticket.co.jp/ [its really expensive]. here few of my advise for anyone who want to buy Arashi concert tickets.
1. Buy the ticket after the seating plan is known. Do not buy ticket before you know where is the seating plan. It safer for us as a buyer. Because you may pay a lot for back seat tickets.
2. Buy the ticket near the concert date.
http://www.ticket.co.jp/ have a policy to stop the concert ticket sales 5 days before the concert. Is the best time to buy the ticket. There is so many people that can help you. Look at je-sales@lj for several account that dealing with ticket.co.jp [remember to pay the extra money for web fee and service fee].
3. If you missed the ticket.co.jp [it happened to me once], try yahoo auctions. With the sites fully in Japanese language its not easy for us but no worries
http://www.fromjapan.co.jp/ can help you. Using this site a lot more cheaper rather than using other service. They can sent the ticket to your hotel.
4. To find the right auctions at yahoo.co.jp please go to
http://www.1945.jp/personal/a_/arashi/arashi-yahooac-day.html this helpfull website aready divided arashi ticket based on section.
5. Is not official but, try other dome than tokyo. Fukuoka and Sapporo could be an option.
6. There are a lot of people that sell their ticket on the concert day. Usually they stand on the way/near the dome. However, I would not recommend this one simply because I could not speak Japanese properly :D
7. Check the dome map. And try to find out where you seat.
Any question please pm me :) and good luck :D