The first part of my M&G takes place outside, introducing the dogs and taking them for a walk to get acquainted, so I don't have an opportunity to take a lot of notes. I like to ask the owner a lot of general questions about themselves, their dog, where they are going, etc. It shows an interest in them and their dog, and often things come up that you might not have learned otherwise. I'll also talk about myself and my dogs a bit, to give them a feel for my style. Clients usually ask me the same general questions - where I work, how long I've been in Portland, how long I've been using Rover, etc. I get to observe how they are with their dog, and how their dog responds out in public, and vice versa.
Then once we get back to my house I ask them more specific, detail-oriented questions regarding their dog's care. If something important has come up on the walk, I can ask more about it to make sure I'm clear. Some things I might not have thought to ask my first time include asking about where the dog usually sleeps (I don't allow dogs in my bedroom, and this can cause some anxiety to dogs who are used to sleeping with their owners), whether or not they are allowed to have treats during the say and if they have any allergies, and whether or not they are inclined to bark/whine/howl, and what they normally do to prevent it.
Good luck with the M&G!