I have to agree with the walk in method. The bad time to walk in is during lunch or dinner service. So before 11 o'clock and after 2pm but before 5pm. I would consider this common sense but perhaps it isn't. You don't walk in during service and service times are the same everywhere.
When someone called our restaurant for a job, I always told them they had to fill out an application. I would not say whether or not we were hiring, just that they had to fill out the application.
If and when they showed up, they actually made the effort to come down and I got to see them in person. Were they well groomed and presentable? Had they made an effort to look like they wanted to impress? Not suit and tie, just clean, neat, decent clothing, shirt tucked in, no funky t-shirts.
Ability to fill out the application shows ability to follow simple directions, read and write. A quick glance for those qualities usually told me all I needed to know. Did I get a firm handshake and a look in the eye? Were they articulate or mumbled?
The saying "a picture is worth a thousand words" held true for me.
So you could call to verify when the chef will be there and not taking a day off, but in my experience, nothing beats showing up.