Is it the composition of the tire material, how many "ply," the TPI? How do I know which tires will be longer lasting and/or less prone to flats? There are so many brands, and so much manufacturer hype, that it makes it really hard to figure out for this newbie to road cycling. Mountain biking is pretty easy--I just pick the nobbies that match the terrain. So what criteria do I use to select my road tires?

It's a variety of factors, even where you live is a factor, as is how often you don't mind getting a flat. IMHO I'd find tires you like and see what the reviews say about puncture resistance.

Since tires are truly an expendable item, many people buy them when they can find an acceptable tire on sale rather than obsessing about meaningless minutae of thread counts and tread compounds. Even with the same tire, some people have lots of flats while others have virtually none. This is a combination of road conditions and rider skill in avoiding hazards. If you live in a truly rugged environment, you might consider something like a Specialized Armadillo, while others would recommend tire liners or thorn-proof tubes, and still others go with the Specialized Airloc tubes. Lots of advocates for each choice. Realistically, you cannot tell tire durability by reading specification sheets.

More material of a harder nature makes tires durable. Unfortunately, grip is less, and the tire conforms to the ground a bit less well. That makes it harsh.

Less material, softer material in a tire gives more grip, supple feel at higher pressures.

Thanks for your comments guys, good food for thought. I think I'll just watch for sales on some decent name brand tires. Experience may be my best teacher.