Write the context down while you are still there
The single sentence that makes a follow-up work is not their job title. It is what they were excited about, what they were struggling with, or what you agreed to send them.
Capture it within minutes. By the next morning you will have compressed six conversations into one blurry memory of a room.
Follow up within three days
There is a window in which they still remember your face. Inside it, a short message is welcome. Outside it, you are reintroducing yourself and the message has to work much harder.
Three days is a good default: long enough not to seem frantic, short enough that the conversation is still live for both of you.
Reference the conversation, not the event
"Great to meet you at the summit" tells them nothing and could have been sent to two hundred people. "You mentioned you were rebuilding onboarding — here is the piece I said I would send" proves you listened.
This is why the note matters more than the reminder. The reminder gets you to write; the note determines whether the message lands.
Decide the next horizon immediately
When you send the message, set the next touchpoint. Most relationships die not from a missed first follow-up but from an absent second one.
A quarterly check-in with genuine context is enough to keep most professional relationships alive indefinitely.