What are the best criteria to select the employee of the month ?

KRAs (key Result Areas) and KPIs (Key Performance Indicators) are identified through the job descriptions and are best to evaluate performance.
The employees with highest score on achieving objectives can be considered for employee of the month.
.

by using ERP like SAP, Oracle, BMC, you can track job opening and closing for all employees in your organization, hence, the highest number of jobs closed at deadline belong to the superior employee of the month.
Regards, Ahmed

Thanks to all, in my point of view productivity is the key value, however in KPIs its measured the overall year performance hence its not applicable in monthly basis.
example of critieria can be taken into consideration such as: Productivity - attendance - punctuality - creativity - internal & external customer focus.