Ray,
There is no quick fix when it comes to QDM. Timbercruiser hit the mail on the head about deer age and genetics. Providing a good yearround nutritional source of protein and letting the younger smaller(1, 2 and 3 1/2 yr old ) deer walk will allow you to get the maximum out of the genetics in your area.
If your property is not very large and there is hunting on the neighboring properties, it may be very hard to control the age of the surviving deer unless your neighbors agree to let the younger deer walk also.