In the sports world effective preventive strategies include teaching proper deceleration techniques (both vertical and horizontal) since many of the non-contact ACL injuries occur during a ‘deceleration event’ such as stopping, landing, and cutting (e.g. teaching triple-flexion upon landing to help avoid valgus and stiff-legged landings, and teaching proper control of the center of gravity upon cutting and stopping are two primary teaching tools to help reduce this risk). Also improving hamstring strength (i.e. the hamstring to quad strength ratio), and improving proprioception (through such techniques as pertubation training) are very useful in decreasing the risk of non-contact ACL injuries.
For contact ACL injuries there’s not a lot that can be done from a training perspective that can be done to reduce the risk since it’s the contact that is causing the injury and only things like equipment etc. may help reduce that risk.