For Japan visitors, Tsukiji market would be the highlight in their whole tour even though not many Japanese people visit Tsukiji for sightseeing. So I tried visiting Tsukiji tuna auction as a tourist, and it was very fun!
In fact, I got on the first train and had been there before, but I was too late. If you want to see the tuna auction for sure, you should arrive at the market gate by 4:00 am. So the transportation available is only taxi. Please make sure to tell the taxi driver that you want to go to Kachidoki Gate or Fish Information Center because Tsukiji market is so huge and has some gates.
On the 2nd try, I arrived at 4:15 a.m. and finally got in the tuna auction line. For this auction, number of visitors are limited up to 120 people per day, on a first-come, first-served basis. You cannot make reservation or you cannot get in line for your friends. Visitors who want to see the auction have to come early for registration and wait for a long time. The registration time is from 5:00 am. First 60 people visit the auction area from 5:25 am to 5:50 am, and second 60 people visit there from 5:50 am to 6:15 am. I got in the second group, and I had to wait from 4:15 am till 5:50 am. I could get inside of Fish Information Center from 5:25 am, but I waited outside till then. So please make sure to bring a warm jacket with you if you go in winter. Please do not get sick during Japan visit. At the Fish Information Center, you watch the video for visiting guidance.
OK! Finally our time. Wearing highlighted vests, 2nd group got inside of the market. The market is full of business people, it is very busy and crowded with trucks, forklifts, and turrets (in the photo left). They have the rights of the way. Please be very careful not to be run over by them!
You can watch the tuna auction from visitors' designated area. If fact, second group could see the auction for bigger tunas even though the group has to wait longer. (You cannot choose the group when you get in line though.) The tunas you can see are all frozen tunas.
At the auction area, brokers are checking the tunas' cut tail fins to check the grade before auction. They lit up the meat and check the color and fat. 
Now the auction starts with a bell ringing. The seller and buyers use their fingers to show their bidding prices. You can take photos of them, but NO flash because it might interfere the their businesses. This is not a show, but real business trading. Please enjoy watching their serious process. When the buyer is selected, the seller calls the buyer's company name and goes next.
At 6:15 am, 2nd group leaves the auction area. You can see the tunas are carried to buyers' stands and cut in their kitchens. After tuna auction, you have to leave this area, but can come back to wholesalers' area at 9:00 am.
I was amazed that Styrofoam boxes were stacked high! There is a small factory to recycle these boxes here. In order to avoid any fires, buyers are supposed to bring their all boxes after. You must be very tired and feel freezing if it is winter. Let's get warmed. This Ramen noodle shop Inoue has always many people in line, but you will not wait long. On this day, I waited about 15 minutes.
The noodles in soup are topped with big slices of roast pork with some vegetables. Get energy here and start the day, or... go back to hotel and take a nap. (I took a nap...)
** Caution **
Tsukiji market is very crowded during the year-end and New Year. Therefore the Tuna Auction Observation Area is temporally closed. You cannot visit Tuna auction to ensure the safety from Dec1 to Jan 19, 2013. (This is the rule of every year.)
** Updates **
In the first tuna auction at Tsukiji Fish Market in 2013, the highest price of the tuna was JPY150,000,000 (about 1.8 million USD) for 222kg !! The restaurant Sushi Zanmai bought the tuna, and it was the big news in Japan.http://www.tsukiji-market.or.jp/tukiji_e.htm
Please be careful and Experience Japan!
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