The first follow-up: A thank you This is sadly becoming a bygone practice, but I'm still a little old school. I don't think you have to thank every person for every meeting with you (particularly business meetings among peers). But I do think, if you're the one who initiated and you're the one who requested advice, it's very appropriate to send a note the next day.
The second follow-up: 3-6 weeks later This is the one that really lands for me but the one so few people tend to do. Let's be honest: We're busy people and sometimes I forget someone I met last month -- particularly if I was in any way feeling rushed or busy that day. But this allows just enough time to pass that you're not annoying, but also guaranteeing that I'll still have some memory of what we spoke about. This is also the easiest layup of a follow-up to do: Just tell me how things went with whatever we talked about. Did you have the conversation with your manager? Decide to go down a different path in your career? Did you meet with other VCs and accept a term sheet? Even if you didn't take any advice I gave you, if you're interested in staying connected, this is the surefire way to get that foot in the door.
The third follow-up: 4-6 months later After the one-two punch of the first two, you can start to ease up on your cadence of communications. I do think one additional touchbase a couple of months later is the best way to stay on someone's radar at least throughout a single six-month period. (Therefore maximizing their odd that they will remember you when it counts.) For this one, you have a few options: Check in again about that thing you spoke about before (but only share meaningful updates here), or maybe spend 5-10 minutes seeing what they've been up to online during this time and try to offer them something in return. Maybe they launched a new business or took on a new role. Maybe you saw they moved to a new city and you just want to drop them a restaurant recommendation of a place you love. Doesn't have to be anything major. But it does have to be impactful. After this period -- three touchpoints over six month, you've set yourself up for a long relationship ahead. (Assuming, of course that your emails are being received and responded to.) After this point, in another 6-12 months, for instance, you can likely invite that person out for coffee and they'll say yes. You can ping them again to check in on something else. You can offer your help or network on a new project they are working on. All the great things you probably do already with any professional connections. If this seems simple, it's because it is. Just set reminders, stay in touch, and you'll see the benefits pay off. If this seems hard, it's because it is. With a million different things flying around, who's got the time and energy to put toward this type of thing? I'll tell you who -- people who are serious about the trajectory of their careers and businesses. And that could be you, too.