The simple answer is, to steal Nike's thunder: just do it. Remember that your shoes are dumb objects. They can't tell your body how to move through the gait cycle, and they can't dictate how you will land in your footwear. So the idea that you should be going out and buying different shoes right out of the gate (as advocated in this book) is absurd at best, and downright dangerous at worst.
How can it be dangerous? Well, let's think about this as if you have been happily heel-striking your way through miserable miles. You've been transmitting the majority of the shock through initial impact through the heel, which brings that up through to the upper part of the leg, causing more strain on the knee and quadriceps. As you start to move towards midfoot, the Achilles' begins to lengthen slightly, and the strain begins to be placed on the calf. You then utilize this muscular grouping through the rest of the gait cycle. So simply, you've got two different groupings taking care of the three phases of the gait cycle: heel/knees/quads for the initial impact, then calf/Achilles/foot for the transition and propulsive phases.
When you midfoot strike, though, you're changing the emphasis to more of the latter, and a lot less of the former. Much like the first few weeks when you hit the gym, you'll be sore as all hell. The problem that seems to be coming up, though, is too much emphasis on the Achilles/calf. This usually happens because people are landing too far forward on the foot, avoiding the heel entirely. We're designed to use both systems; why else would we have them?
As such, there are four main categories of footwear on the market. It doesn't help that a lot of the companies that are making shoes don't seem to be able to come to a consensus as to what to call it all. So, I'll do them a favor, and do it for them.
Natural: Natural running shoes are not necessarily minimalistic running shoes. Instead, natural running shoes attempt to put your foot into a similar position as if it were barefoot. However, as covered in the previous post, most of us do not have the bone density to be running on pavement every day barefoot. As this is the case, these shoes tend to have cushioning along the same lines as a traditional training shoe. Look for less heel-toe drop in the shoe (under 6 mm, give or take), but plenty of substantial cushioning. Who it's for: runners who have converted to a midfoot strike with no issues; former track runners who have maintained a forward technique; neutral runners looking for a true "flat" for racing. Examples: Saucony ProGrid Kinvara, Newton Gravity, New Balance Road Minimus (name may change, available 3/1/11).
Minimal: Minimal running shoes are merely stripping away at the cushioning underneath the foot. They are trying to providing much more feedback as to the surface you are on. Some would advocate that this teaches you to be lighter on the foot. Your results may vary, but my experience is that these are for people that don't like much shoe underneath them AND have a pretty good bone density. A lot of minimal shoes will still have a pretty high heel-toe drop, though, and will let you land on your heel if you decide to. This is where most "racing flats" these days fall. Who it's for: runners seeking as much road feel as possible; runners seeking a short-distance racer; a runner looking for a speedwork shoe. Examples: New Balance MT101, Brooks T6 Racer, Nike LunaRacer, Nike Free Run.
Barefoot: Zip. Zilch. Nada. Nothing going on under the foot outside of maybe 3-4mm of foam. There's really only two things that fit into this category, no matter what shoe companies will try and tell you. Most people will never be able to use these as their primary footwear solution; however, again, results can and will vary depending on body weight, surfaces used, impact force generated while running, etc. Who it's for: someone looking to begin incorporating barefoot technique into their repertoire, but want something to actually protect the foot in the process from sharp objects; trail runners. Examples: Vibram Five Fingers (KSO/Sprint/Flow for off-road; Bikila for on road), Merrell Barefoot Collection (tentative 2/1 release; partnership with Vibram...so for those who can't stand the toe-separation, here you go!)
Traditional: Big old wedge shape here. Not that it's a bad thing, but will tolerate higher load-stresses on the heel. You can still wind up getting relatively lightweight here as well, but not quite to the same degrees as the categories listed above. Remember, though, that weight only matters when your foot is working efficiently. If in this category, it'll be imperative to get fitted for the correct amount of pronation control (such as this fine-fitting institution). Oversupporting the foot can be just as poor as undersupporting it. Who it's for: heel-strikers; midfoot/forefoot strikers who are running into Achilles and calf issues; those who don't want to change how they run period. Examples (ranging from least pronation control to most): Brooks Launch, Mizuno Wave Rider 14, Saucony ProGrid Guide 3, Brooks Adrenaline GTS 11
So, armed with this information, where do you go now? Start with the light barefoot work and see where it takes you. Listen to what your body is telling you; it will give you the keys as to which of these four categories you will best fit into.
And remember, have fun out there!