Scheduling of jobs has a significant contribution to the improved performance of the job shop production system. This study is aimed at developing efficient priority dispatching rules (PDRs) for scheduling in a job shop to improve the tardiness and flow time performance measures. The selection of PDRs depends on the scheduling criteria and job shop conditions. LEKIN software can be used for a variety of well known job shop conditions and varying flexibility. Different schedules are derived using the LEKIN scheduling software for different PDRs such as earliest due date and shortest processing time. In this work, seven static dispatching rules have been taken from the literature study, and four new priority dispatching rules have been proposed and compared to schedule two formal job shop problems under four objective functions, whose aim is to improve the performance measures. The results show that the proposed PDRs are very effective in minimizing various performance measures.