Just to add a practice I do when shooting a Commerical Real Estate project. I go in to the business and introduce myself and explain why I am on their property - to photograph the property which includes areial images using a drone, so if anyone comes in and tells you that there's a guy out there with a drone you can tell them why.
I have found that this approach negates a lot of confrontation with commercial real estate. If the store manager asks why, or who sent me, I explain that I have been sub contracted by a company your corporate office hired. They don't tell me the "why" just the "what". Usually, they want images for advertising, marketing, insurance, or they may be selling. They don't share that information with me. This usually satisfies them and I continue to do my job.
Of the 15 plus years that I've been doing this and using this approach I have had only one issue to occur and that was with a District Manager of a Oil Changing Company (chain). One phone call to his boss set him straight.
I know that are those that feel that don't need to let anyone know what they are doing and taking the time to use my method does take extra time, for me, I have found it to be the best method.
When I first started in the business, I would just show up and start my work, and without fail, I would have to stop to explain myself, not a negative confrontation, just a "need to know' what you're doing visit. This actually took longer than my going in and explaining from the beginning.
Whatever works for you, do. Just be professional, civil, and most of all, legal.