What is the best way to run to your fastest while simultaneously putting you at limited possible risk of injury? It has been a hot topic of debate. At the forefront of current research are efforts to discern what the primary biomechanical factors are that can and should be changed to achieve optimal performance and minimal injury. 
One of these factors is how a runner's foot strikes the ground. Working as a physical therapist, one of the first questions I now ask my patients is how they strike the ground with their feet. Fifteen years ago, I would have not asked this question. It was presumed if you were a runner or an athlete you ran like most of us walk -- which is striking with the heel first.
Head coach of the Nike Oregon Project, Alberto Salazar, tasked with trying to reestablish America's competitive long distance running athletes, is a proponent of trying to change the biomechanics of long distance runners.
Prior to inducing a biomechanical and purposeful change in an injured runner, it is essential to first determine what is inducing their injury. Sometimes it's overuse, training errors (not enough cross-training), poor sneaker choice for their respective foot type, weakness along the kinetic chain, or just bad form. The ethos behind biomechanical changes with footstrike is basically to minimize load on the lower body. However, one needs to figure out what is the best means of doing so on each patient's individual morphological makeup. If a runner has chosen to change his/her footstrike to decrease stress on the knees, he/she needs to know this will impact all of the other moving parts in the kinetic chain. Dr. Heiderscheit, associate editor for the Journal of Orthopaedic and Sports Physical Therapy, in his editorial states: "With the interdependence of these kinematic factors it is difficult to change one without inducing change on another."  Researchers Cavanagh and Williams found that runners typically have the best economy of effort as measured by oxygen consumption when they run with their "preferred pattern."  Therefore, it is not always easy to change the way we run and land to avoid pain and most individuals go back to their preferred pattern of running and may not reduce their injury risk.
A growing consensus is that runners who land with heelstrike or rearfoot have increased impact loading at the knee and patellofemoral joint. Individuals with knee pain from running may benefit from trying to land on their midfoot or forefoot.  Other research has found that those with forefoot landing increased the vertical loading on their calf muscles. That said, those with a history of achilles or foot pain may need to reconsider their striking pattern to a heel strike pattern.
It is too soon to tell the most ideal landing and running patterns. Each person's genetic makeup is unique as is their biomechanical alignment. Thus, I believe it is important to try to use a few basic tenets to help prevent injury. I have listed them below in bullet form, but once an individual has suffered an injury, it is important that they see a specialist to help them uncover what has lead to their injury and reduce risk of re-injury.
* Cross-training is essential -- meaning using a bike, swimming or elliptical to work on cardiovascular fitness, not just running. It also means weight training especially for strengthening the hip abductors, hip external rotators, hip extensors and quadriceps (but NO leg extension machine in the gym, as it will hasten patellar cartilage stress) and core.
*Stretching -- Active stretching pre-running and static stretching post-running.
*Wearing good supportive sneakers -- I like New Balance, Brooks and Asics. It is generally suggested to change to new sneaker every 250-300 miles of running.
I am not a proponent of the trend to use "barefoot-minimally" stable sneakers. Those who are running totally barefoot are in my opinion only hastening the risk of tissue breakdown and injury
*Be methodical -- Monitor your miles or time your running and go up in in a pragmatic way to avoid overuse injury, avoid consecutive days of running especially in the beginning to help decrease injury as tissue accommodates to new stress. Use off-running days to do your cross-training
*Alter your terrain if possible -- Try running on grass or cinder track as opposed to always on concrete streets to decrease shock to your joints
*Remember your posture while running -- Best economy of effort is an aligned body and arms in close to your sides with gentle rotation of the arm swing, which induces better trunk rotation.
*Never hurts to ice those knees 10-15 minutes after a run for reducing any post-exercise inflammation
1) Heidescheit B, editorial, Gait retraining for runners: In search of the ideal. J Orthop Phys Ther.2011; 41: 909-910.
2) Cavangh PR, Williams KR. The effect of stride length variation on oxygen uptake during distance running. Med Sci Sports Exerc.1982;14:30-35
3) Cheung RTH, Davis IS. Landing pattern modifications to improve patellofemoral pain in runners: a case series. J Orthop Sports Phys Ther.201;41:914-919