What are the main skills that every warehouse supervisor must have to excel or succeed?

The required skills could be divided into two kind of skills: personal skills, and managerial and scientific skills.
Both of them are possible to be gained, according to the willing of the supervisor.
The personal skills: the wisdom of the supervisor in dealing with the store keeper and workers.
Reading and understanding few books about human resources and the psychology of workers, will make you able to initiate and motivate them to follow the plans drawn.
The managerial and scientific skills in the field of warehouse management: here you have to study and implement few things like: - The knowledge with Products themselves and their MSDS as well.
- the Software that organizes the warehouse activities: ERP, SAP ....
- Coordination and continuous meetings with any related department: finance, production, sales, maintenance.
Finally, regardless to your knowledge with warehouse management, reading newest books and attending courses about warehouse management are good idea to keep your information updated,.

I would suggest the following   compliance on receiving and issuance ( and any other activity, eg returns, etc) procedure fully Understanding of all SKUs and their storage requirment stock managment and enusre safety stock levels and keep update stock levels in software Command of inventory software which is used by comany keep motivating the staff and engage them maximum Regular stock takes to avoid losses