Ask HN: What tools do you use to manage relationships?

I've been thinking a lot lately about how to maintain relationships with "weak" connections (former colleagues, classmates, etc...). I think they can be very valuable and I'd like to stay in touch but don't really want to reach out and see if they want to hang out on a Saturday night so having them in my phone contacts seems a bit much.

I think it is important to take notes to help remember things to bring up later like things about family, hobbies, etc...

What tools do people use to manage these connections? Does anyone use any tools or am I over-thinking this?