I am not an expert, but I can answer a few of your questions from above...
At a cat show, the breeders exhibit their cats, if you went to one you could look around at all of the siamese on exhibit there and see what you like in person and get a feel for their personalities. It will also give you a chance to meet the breeders in person and get business cards or probably even set up a visit to their cattery. Although some breeders might bring a cat that they are interested in rehoming/selling to a show, a good breeder wouldn't sell to you at the show and would require references, etc.
A good breeder will also have a contract that you must sign that specifies things like returning the cat to them if you can't keep it or if it has a medical problem and requiring you to get it spayed/neutered. They should also not shy away from you going to their cattery in person.
CFA, ACA, TICA- are all cat show/registration organizations and the FBRL: http://www.breedlist.com/
is a list of breeders and breed information (it is not affiliated with a specific cat show organization).
Another good source of information is the "breed council" on the breed you're interested in, I know you can find the siamese breed council as a link off of the CFA siamese breed description. Many times the breed council can give you a list of breeders in good standing on the breed council if you contact them.
Another thing to look for (at least with CFA) is when a cattery gets a "cattery of excellence" award. This means that the cattery has met certain standards and is in good standing with that organization.
I am sorry that I can't help with the other initials you listed, as I'm not familiar with them.
Another note, some breeders register with multiple cat show organizations, so that shouldn't be a turn-off for you. They do that so that if you buy a cat from them you can show it in either organization.