Say you get in to work on a Monday at 9 AM - what does your day look like, and your overall week? This of course depends on what their role is; for example, if they're primarily doing content marketing and blogging, I'd ask them, How do you determine what to write about next? How do you prioritize tasks? If you're a link builder, I'd ask, How do you prioritize your link opportunities? This is super important because in SEO, you have an infinite number of things you could potentially do on any given day, and only 8-10 hours in the day to get something done. I want to see their attack plan. They should have an internal system and be able to take initiative - I don't want to hire an SEO who needs constant hand-holding from a manager.