"Easy, then light, then smooth, then fast."
-Micah True (a.k.a.- Caballo Blanco)
When people ask how to start barefoot running, Caballo Blanco's advice to Christopher McDougall in 'Born to Run" is nearly perfect.
Easy: When first starting barefoot running, it is critical to start slow and relaxed (easy). Proper form is impossible to achieve without relaxation.
Light: Once you learn to run relaxed, you have to learn to run light. You should make little or no discernible sound when your feet touch the ground. The foot/ground contact should be a light kissing... almost as if you were floating over the ground. This insures you run "light".
Smooth: After you can run relaxed and softly, learn to run with great efficiency. Every movement should serve a purpose with no wasted movement. Your upper body should barely move as your lower body effortlessly navigates the terrain under foot.
Fast: Once the first three are met, speed will take care of itself (to paraphrase C.B.). Speed is a function of excellent form. The other three elements will guarantee excellent form.