How would you approach a situation where you would have an hour for a lunch with a girl and use it as a building block for next time when you have more time with her? Next time as in weeks or months.

I am about to meet a former coworker, which I saw last time about a year ago and have had a minimal contact with her. I know I have to see her first and go with the situation/vibe, but still, this is a scenario with which I am not familiar.

It not necessarily only for this specific case, because I have other "friends" in different cities/countries that I made during my studying or working abroad.