1. A computer-assisted method of selecting and optimizing a drilling bit for drilling an identified target hole section of earth containing at least one formation, the method comprising the steps of: determining a formation property value for each member of a set of a plurality of formation properties for each formation forming the target hole section to thereby define at least one set of formation properties; determining a drillability parameter value of each member of a set of individual formation drillability parameters for each separate one of the plurality of formations forming the target hole section responsive to the plurality of sets of formation properties to thereby define a plurality of sets of individual formation drillability parameters; combining each of the plurality of sets of individual formation drillability parameters to thereby represent the target hole section with a set of combined drillability parameters; determining a performance attribute value for each of a plurality of performance attributes describing target hole section performance requirements of the target hole section for drilling the target hole section responsive to the set of combined drillability parameters to thereby define a set of target hole section performance requirements; determining a performance attribute value of each of a plurality of performance attributes describing drilling system performance characteristics associated with a preselected drilling system for drilling the target hole section to thereby define a set of drilling system performance characteristics; combining the set of target hole section performance requirements and the set of drilling system performance characteristics; and responsive to the step of combining the set of target hole section performance requirements and the set of drilling system performance characteristics, determining a performance attribute value for each of a plurality of performance attributes describing performance characteristics of an optimal drilling bit for drilling the target hole section with the preselected drilling system to thereby define a set of drilling application performance requirements.