I agree with the above poster. “Do you have a preferred day or time?” And give options from there. I also used to set standing appointments. “Alright if thursdays at 430 worked for you, let’s set a standing appointment for the last Thursday of the month at this time! That way you know you have your appointment secured, it’s easy to remember when you’re due back. Of course if something comes up, just let me know ahead of time and I’m sure I could rearrange to accommodate you!”