How does one get started in search and rescue dog training?

The reality of the breed choice is usually the handler.  Essentially you need an intelligent, biddable, confident dog with excellent physical structure and enough leg to cover ground quickly and efficiently.  That usually means herding, working and sporting dogs, but it certainly would not exclude any other breed.  Some organizations and handlers start with puppies, others with shelter dogs (many dogs in shelters are often there due to poor fit within the family and a high level of drive)

You need to be part of group since the need for equipement and access to sites is critical.  A google search on SAR dogs will give you a number of links.  Using the non emergency line for you local fire/emergency folk or law enforcement will usually get you a contact number of any local certified SAR folk.

SAR is typically divided into two sets of certification but it is not limited, you can go between disciplines.  There is the set of wilderness skills which include water, avalanche, etc.  Then there are the urban skills.  In addition there are detection skills like article finds and cadaver locations.

SAR is fairly expensive at a personal level with respect to money and time.

I have the dog with drive, and I have the interest, but I certainly don't have the time and may not have the money, in addition to being too old to climb over rubble LOL.
But, even if any of that's the case with you, when you assess what this will require, don't give up wanting a dog that can search.  There's always tracking competition, or location of lost pets, as a substitute.  Google on "Kat Albrecht" for the latter.
Good luck - I hope you do get to do SAR!

I'm 17 and not doing SAR yet, but I rescue dogs and have experience with therapy/service dogs. Golden Retrievers and Poodles with correct structure, temperament, and drives are perfect for SAR. Goldens are fairly common, actually. Both breeds are intended to brave the elements as bird hunting dogs. Many mutts, however, also have all the stamina, agility, intelligence, and perseverence necessary for SAR. As far as purebreds go, however, my breed of choice would be the American Staffordshire Terrier (or rescued "pit bull" type dogs that have their size and qualities). They have the tenacity, devotion, rock-solid temperaments (when bred and trained properly), agility, stamina, high pain threshold, and power in a small package (compared to GSDs and retrievers). They can squeeze through tiny spaces, climb through rubble, be lifted easily (important for going down on a rope, etc.), and snuggle in your lap after a hard day's work. Also very clean.

If you don't yet have a dog and are set on it working in SAR (as opposed to simply a pet), I highly advise you think carefully before purchasing a young puppy. Even with a pup from a serious hobby breeder, you don't know that this particular pup will grow up healthy and suitable for SAR. If you want to purchase from a breeder, find one who shows successfully in dog sports (eg: Goldens might hunt, GSDs might herd, all might do obedience, agility, tracking, etc.) and/or SAR, not just conformation. You can also save a dog's life by adopting from a shelter or rescue. These dogs are by no means "bad". A fine example is MACH Little Shepherd Girl, a rescued GSD currently ranked around #5 agility dog in her breed. There are also 3 "pit bull" type dogs - Cheyenne, Dakota, and Tahoe - that are featured online at www.forpitssake.org. I like this site for SAR info in general. Rescuing a young dog (~ 6 months - 2 years) can be very rewarding. Just make sure they're well evaluated.

I personally would recommend spending a lot of time with a variety of dogs (eg: animal shelter or rescue), teaching them tricks, etc., just getting used to them and figuring out exactly what YOU can deal with in a dog (that's how I found out that a 75-lb 14-year-old can pick up a 30-lb pit bull but not an 80-lb Golden!).

Yah I work in a vet clinic so I'm used to seeing all sorts of different temperments, behaviors, weight ranges, how to handle variouis animals, etc and so forth. 

The thing I'm not used to is training them for agility.  I've always just had dogs as pets.  Teach them how to fetch, come, sit, stay, lay down, how to walk off leash, play frisbee, simple stuff like that.  How to sniff out a human being under rubble?  Eh not so much. 

Directional commands are not difficult to teach.  Use the strategies for directional commands with gun dogs, or herding dogs, or sleding dogs.  You need to be able to move left, right, forward and back.  You need to be able to do it at a distance.  The tunneling, climbing etc.  will not need to be taught to a high drive dog,  you want their nose to decide how to approach the rubble any way.
 
You could check out a website a friend of mine has,  she is in SAR.    [linkhttp://www.bigmtnbelgians.com/]http://www.bigmtnbelgians.com/[/link]  She has links for other SAR sites as well.