İ start swearing them. Then they respond me back with the same then we're good to go

I typically check in on them every two weeks or so. For those who I'm rather close with, I typically text them once in a couple of days to ensure that they are doing well. It really depends on how close of a relationship we have. I can completely understand if long-distance friendships are rather difficult to keep in touch, but I'd like to believe that I'm attempting my best.

WhatsApp I keep in touch by

Whatsapp mostly, or Twitter because many of them are friends from social media

We actually became pen-pals!