During a tenancy
After your new tenants have moved in you will have to carry out periodic checks. The frequency of these checks will vary with the type of tenants (e.g. a single person, couple, family or house in multiple occupation (HMO) with different households in different rooms).
When you carry out these checks you should keep a written record as, not only will it enable you to demonstrate that you are properly managing your property, it can also be useful at identifying problems before they get too serious or become costly to fix.
The maintaining good standards in your rented property page has much more information about some of the technical and legal issues when renting out your property.