<human>: (Adding the Dating flair because I am attracted to him, but advice for developing a platonic friendship is welcome too)

I don't know how seriously posts about grad students and their professors are usually taken, so here are a few things I thought I should address before continuing:

* Yes, he is a lot older. I'm comfortable with this.
* All our interactions to date have been strictly professional. We've never flirted and in fact I didn't even find him attractive until just a month ago.
* He's divorced with no kids and has no committed relationship at the moment.
* There are no policies against faculty/postgrad relations at the school and we are both leaving anyway. Grades have already been finalized.
* He was not my thesis advisor and I will not be asking him for references.
* I will not be working in the same field as him.

I also want to make clear the fact that at this moment in time, I'm not so much head over heels for him as I am interested to first find out more about him on a personal level.

He actually invited me to a casual meal recently (he wanted to get to know me better outside the classroom) where we talked mostly about my future plans and political/social issues. It was all very enjoyable and we appear to share a lot in common in terms of hobbies and values, so it would be nice to explore things further in a non-academic context.

I did pick up from our chat the sense that he'd be equally interested in at least becoming friends, e.g. joking that I should visit him at his new workplace and asking for my Facebook. I guess my question is what should be my next step? I've never asked a guy out before and while I'm not scared to do it, I'd like to be as subtle as possible without making things awkward.

Provide a brief overview of the text.
<bot>: I want to ask my graduate school prof out now that grades are in and there is no conflict of interest at all. How can I be direct and subtle at the same time in case he just wants to be friends?