Argh, now I feel terrible for not explaining stuff.
Go to
www.anime-expo.org, click Registration, then Register Now. It is generally much easier to pre-register; you will get an email later on with a barcode that they will scan when you arrive at the pre-registration line. Nowadays, that should be quicker than buying a pass at the door (since you have to fill out everything on the spot). It's also a little cheaper now too. You need the pass to go into the Exhibit/Merchandise Hall, any panels, and any concerts.
The pre-registration line will be busiest on the first full day, Friday, but will also be somewhat busy on Saturday for the people who aren't attending all 4 days since Saturday and Sunday are the main events. The line to get into the exhibit hall every morning at 10:00 will be LONG, but say you get in line at 9:30, you'll probably be in the hall by 10:30 or 10:45. I don't bother trying to be one of the first people in line anymore. If you're going to buy stuff, keep in mind the vast majority of booths will be selling manga and DVDs. All of them tend to have large discounts on bundles of manga and DVD boxsets. You usually don't have to worry about any of that selling out in the entire Hall unless they are new releases like the latest volume of Negima or something like that.
There are a few Touhou/doujin centric merchandise booths. Hen Da Ne is the one that sticks out in my mind; most well known for the guy screaming out YYYYYYAAAAAAAAAAAAOOOOOOOOOOIIIIIIIIIIIIIIII and selling giant YAOI paddles. There will be some Touhou doujin there. Kinokuniya will have a booth, usually in the middle of the Exhibit Hall with their array of Japanese manga and artbooks. That's one place you might get the official ZUN printed works. If they don't have it there, you can request the cashier to see if they can bring any for the following day. Or just drive to Little Tokyo where the store is (just 10 minutes away from LA Convention Center). I think there are a few other booths that may have Touhou plushies and other small goodies. Be warned it won't be cheap.
BRING CASH!!!Bring enough cash! I usually buy manga and sometimes a few Touhou things or anything else that may catch my eye. I usually bring about $300. Most, but not all vendors accept credit card. And ATM lines SUCK. And I don't really do this, but it makes sense that if you ask an Artist in the Artist Alley for a drawing commission, that you'll have to pay in cash. Do check out the Artist's Alley if you have the time. There are some neat little trinkets or drawings you can get there that will be unlike anything you could buy at the Exhibit Hall. Go early if you want a commissioned work since they need time to get it done.
CONVENTION FOOD IS EXPENSIVE AND OVERCROWDED!!!If you can bring something light to eat and stuff into your pocket or small backpack, that would be best. I usually don't bother eating lunch when I go to AX. That's spending money yo! There's nothing really walking distance from the LA Convention Center either.
I also refer to Cosplay.com's forum for a list of series related cosplay shoots. The primary thread is
here. To reiterate, the Touhou gathering is on Saturday, 1 PM in the West Hall. Memorize or print out the map at the bottom of the first post for general purposes. The last one I went to 2 years ago had people hanging around for almost 2 hours. Bring a camera. If you want to take a picture of someone as you're walking along, ask them politely. If you're at a group shoot, fire away with everybody else.
I do not know if there is a Touhou fan panel this year. And I've never seen one at AX in previous years. I'll look into it later.
Just take it easy and enjoy the atmosphere. And seriously, go to the Kalafina concert. I think it will be awesome. I'm skipping the Masquerade.