Buying Tips
Wanting to buy the manga is one thing; finding it is a totally different story.
I've been buying this kind of manga for a few years now, and what I've seen is that there are 4 ways to buy them:
I'm from the Southern California area, and so all my experiences are with the stores in So. CA. Specifically, the Little Tokyo ones and one in Costa Mesa.
First off, the stores tend to have a very small selection of yaoi comics, if they have it at all. Asahiya and Kinokuniya (in LA) don't have them at all. Kinos used to, but they cleaned them all out and will not take special orders. I figured it was probably because they got complaints about those books.
The Kinos in Costa Mesa has a small section for them. It's very small, and a little hard to find. I'm not sure if they take special orders, but it might be good for getting new releases.
But y'know. Kinos is good for finding toys and stationary. However, if you plan to buy music CDs, please be aware of the markup.
A piece of random advice: if you see the comic you want, or think you might want, BUY IT. Next time you're there, I can guarantee that it won't be there. Yeah, speaking from experience here. Thing is, if you've found that shop, I can guarantee other fangirls will find it and buy that comic you might or might not want.
Again, my experience is with So. CA.
There are several used comic stores within driving distance of each other. To hit them all, you have to be willing to drive an hour or so between a few stores. But it can be done, and is often worth the trip if you are looking for other comics besides yaoi ones.
Before you even think about hitting the stores, let me pass some tips on.
First, the books are arranged by publisher. The fastest way to find the yaoi-ish section is to look for the BBC bindings, like the bright red, blue, or black bindings. They're unmistakeable. Around them will be other yaoi-ish publishers, such as Hanaoto, Wings, Bamboo, Asuka etc. Some of the Asuka books will be right next to the shoujo section, which is very easy to find. HanaYume and Ribon comics are hard to miss.
Know what the size of your comic is. Other than being arranged by publisher and then author, they are arranged by size. If one is a bit outsized, you're going to have to find the section of comics for that size.
Some of the Bamboo Reijin comics are near the men's comic section, if not IN the men's comic section. Dig a bit and be patient, and you can find it. They tend to be near the yaoi-ish section, so you won't have to look far. Be prepared to look like a perv (oh wait, too late); I think the section with these comics will be in the section for graphic comics for guys.
Be patient and persistant. Books tend to be out of order, so keep an eye out.
Always check the $1 section. ALWAYS. And there are several $1 sections, so find the appropriate ones and dig.
Book-off
There is a one in Gardena (1610 West Redondo Beach Blvd, informative page). It has a small selection of blatantly yaoi comics, and large sections of Asuka comics. They also have CDs and artbooks, which are always worth a look. They had a Kizuna artbook once for $8 in good condition.
Also, get their little discount-stamp card for $1. In the long run, it will be worth it. And you can use that card at the OTHER Book-off in Costa Mesa.
The Costa Mesa Book-off (2955 Harbor Blvd) is fairly new (as of April 2003)and looks like they're still unpacking everything. The yaoi section is about the same size as the one in Gardena. That is to say, small. Heh. But it's always worth a look, eh?
Added pluses to this one: It has a video rental store attached. There's a Mitsuwa's in the same corner. Across the street is the aforementioned Kinos. And, it's close to South Coast Plaza for your more conventional shopping needs. Can you say, "Borders" or "Barnes and Nobles"? Oh yeah, baby.
Book Market
Book Market is in Santa Monica (3760 Centinela Avenue), and was still unpacking when we went. Then again, used comic stores are always unpacking. It's a bit disorganized, and the yaoi comics are either arranged together, or stuck in some random-ass places out of order. Very small yaoi selection. Large-ish shoujo section. Many CDs.
I've been doing a lot of purchasing online, because the used stores are very limited and cannot refresh the stock as often as I wish.
Acclimate Solution provides new manga and, for a fee, will translate it for you. I've heard good things about this place.
Amazon Japan should be good for new things. I don't have experience there, not speaking/reading Japanese as I do, but they have an English page to explain shipping rates and such to the Japanese-impaired. This is IMPORTANT, because you have to notice that there is a handling charge of 300yen PER BOOK, on top of the very high shipping.
Aestheticism.com has an online store for new books too. If the comic is graphic, you'll need to register before you can buy anything. Registration consists of sending age-confirming ID via snail mail, so you'll have to wait a few days.
Book Mart sells used manga from Japan and has a searchable interface. I don't like using it for 2 reasons: 1) The server is slow. 2) When you get your results for searches, they list books they don't have. However, they have a large selection of things and may be for ordering varying items.
JPQueen is my favored place for online shopping. The prices are steeper than other used stores, and I sincerely doubt they sell anything for $1, but sometimes, they have new books. Also, the books that are 'B' quality are still in very good condition, with crisp paper and smooth dustjackets. However, please note that 'A' and 'B' condition books cost nearly as much, if not more, than the books would cost in Japan. The cheaper books are definitely the 'C' quality books that have some yellowing on the pages, although they are scarce. The should still be in good condition though. As with Book Mart, the shipping will be steep to ship overseas.
Sasuga Books is based in MA, USA and will ship overseas. Shipping is expensive, which is a downer. I haven't actually ordered anything from them, and the one time I tried, they didn't have the book they listed and they couldn't get the book. They did allow to cancel my entire order, which was nice.
What I highly suggest doing is multitasking while you browse. Compare prices of all the books you want at various stores. I've found that, many times, Amazon.co.jp has new books that are cheaper than the used books at JPQueen. However, there is that 300 yen handling fee (at amazon) per book and possibly the higher shipping rate, so please keep that in mind.
These are a bit iffy. I usually find them by searching for yaoi pages that have links to the webmaster's sale page, or by using google to search for "yaoi manga for sale".
I haven't bought anything from anyone yet. The prices tend to be a bit higher than the used bookstores, so I'd rather check the used stores first.
On the other hand, I have a list of yaoi manga for sale. Okay, I'm sorry. No more plugging.