put everyone's birthday in your calendar, and wish them a happy birthday (at least a text) every year
like their stuff on social media
friendships ebb and flow, as people get married, have kids, get divorced, kids become independent, move away, move back. don't give up on a friend even if they disappear for a few years when they first have kids
try to arrange at least an annual in-person meet up, if in the same city
try to involve them in your interests, and try to take up their interests, or at least be curious
fantasy football is helpful. golf as you get older. baseball games. meet for lunch if you're in their part of town. host parties for events like super bowl, the oscars, stuff like that
Kipchoge broke 2h a few years ago, but it was on a closed, low altitude track, with a fleet of rotating runners in front of him, providing wind blocking/drafting as well as pacing
Amazing these guys did it in a real race with no one in front of them (at the end at least)