Hi, in general, a Procurement policy should support the strategic goals of your organisation, as well as the legal environment you operate in.
A good place to start is your organisation's vision and mission statements, strategic planning documents, CEO reports etc. This will give you a high level insight into the organisation.
From there you should consider the other stakeholders in the organisation. What are they doing to support the strategic goals, how can you support their goals, how can you tie their success into the procurement vision, and therefore into the Procurement policy?
Also, what is your vision for your procurement department? How does this create value for the organisation, what do you need to achieve your goals, and what support do you require?
Once you have a mandate for your vision, how are you going to execute this plan?
Your Procurement policy should include not only commodity management strategies, but also strategies for managing how procurement interacts with the organisation.
David van der Walt