A legal disclaimer
anything open cannot be returned
Shipping Policy - the basics
Having said that, a Shipping Policy is a legally binding document that is meant to establish the legal relations between you and your customers. It is the legal framework for presenting your obligations to your customers, but also to address different possible sicarios that may accrue, and what happens in each and every case.
A Shipping Policy is a good practice and it helps both sides - you and your customers. Your customers may benefit from being informed about what they can expect from your service. You may benefit because people may be likely to shop with you if you have a clear Shipping Policy in place since there won't be any questions about your shipping timeframes or processes.
What to include in the Shipping Policy
Generally speaking, a Shipping Policy often addresses these types of issues: the timeframe for processing orders; the shipping costs; different domestic and international shipping solutions; potential service interruptions; and much much more.