It can be equal parts interesting and awkward to run into a close friend that you lost touch with. In order to reconnect on a deeper level, avoid the general questions about your lives and ask more about what they have learned since you last spoke.
When an old friend sent programmer Paul Ford an email saying hello, he wrote a summary about things he learned instead of giving the standard two-sentence bio (such as field of work and spousal updates):
In the last decade, the things I learned were:
How people are typically kind, except on the public Internet (but privately generous). How too many people borrow tragedy that isn't their own. How to build a giant digital archive from old magazines. How to do it again for a different magazine. How to work with digital things by the hundreds of thousands. How to quit a dream job.
The difference between a website, a collection of websites, an API, a platform, and an ecosystem. How to be the dumbest person in the room without embarrassing myself. How to be the smartest person in the room without embarrassing myself. How to be somewhere in the middle of a room. That I'm not the most interesting person in a room, or the worst person in the world. How not to teach a class.
All of those things have their own stories behind them that offer more opportunities to catch up. While it might seem a bit random to email a former close friend out of the blue, this type of question could start a stimulating conversation if the both of you reconnect and actually want to catch up.