When running barefoot, the foot strike (I prefer the term foot "kiss") often receives unnecessary focus. New barefoot runners will spend so much time trying to master the nuances of the "perfect" foot strike, they will ignore more important elements such as posture, relaxation, etc.
I routinely instruct people to do whatever feels natural. The idea is simple- if you follow my advice of starting on a smooth, hard surface, foot strike will take care of itself. If you land with a heavy heel strike or overstride, pain will ensue. Giving detailed instructions cannot account for the natural variation in anatomy. We're all different. As such, our foot strike will look slightly different.
I land on the lateral side of my sole and roll my foot inward. Others land more towards the center of their midfoot. How you do it is mostly inconsequential as long as you can accurately react to the feedback from your feet.
There is one issue that arises repeatedly. many new barefoot runners (or minimalist shoe runners) have a tendency to tense their calf muscles throughout the gait cycle in an effort to prevent their heel from touching the ground. Generally speaking, this is bad. By keeping your calf muscles actively engaged, you put undue stress on your Achilles tendon and the musculature of the calf. The result can be a damaged Achilles, damaged soleus (or other calf muscles), bone spurs, or plantar pain that is often misinterpreted as plantar fasciitis.
Biomechanically, your feet and legs are not designed to keep the heel off the ground through the gait cycle. Doing so eliminates the effectiveness of the longitudinal and transverse arch, quickly tires the calf muscles, and as previously mentioned, unnecessarily increases the chances of injury. Early on, it will also place added stress on the metatarsal bones of the foot.
Simply put, your heel should always softly touch the ground with each step. The exception to this rule is running fast. As speed increases, there will be a slight natural forward shift in weight that keeps the heel off the ground. The Pose method of running explains this phenomenon especially well.
If you're new to barefoot or minimalist shoe running, please heed this important advice!