On Numonday you can set a Privacy Policy, Terms and conditions, Shipping policy and Return policy.
These policies display on all of your products under the policy tab.
Privacy Policy - best practice is to state you will only use a customers details for order discussions and their data will not be used in any other way.
Terms and Conditions - best practice is to include what your terms and conditions are for your products.
Shipping Policy - best practice is to include how you ship the products and how long deliveries will take for orders.
Return Policy - best practice is to include whether you accept returns or not.