1. Keep in touch through voice memos rather than text messages.
2. Create a collaborative playlist on Spotify and regularly add your favorite songs for them to listen to.
3. Try out Rabb.it, which allows you to watch the same TV show or movie as someone else, while you video chat.
4. Send them cards on holidays, birthdays, and other special occasions.
5. Set up your "close friends" on Instagram stories and share updates you'd never normally post.
6. Set up a group chat on every social media platform you use regularly, like Instagram, Facebook, Snapchat, and WhatsApp.
7. Venmo them some money on days you'd treat them to a coffee or wine if you lived in the same place.
8. If you're both into gaming, try playing together as often as you can.
9. Send your friend little things from the place you live to remind them of you.
10. Make an effort to learn little things about the place they live, if you aren't familiar with it.
11. Don't stop making plans, even if they won't actually happen for a really long time.
12. Send them links to things that remind you of them, like funny tweets or articles.
13. Set a standing phone call date and stick to it, whether you can talk for two minutes or two hours.
14. Take the time to send a hand-written letter.
15. And add a Polaroid photo to your letter before you put it in the post.
16. Try reading the same book at the same time, and chat about characters and plot twists as you go.
17. Try and call your friend whenever you're in the grocery store, and ask them to do the same.
18. If your friend lives in a different time zone, set their time in your phone, so you always know if it's a good time to text or call.
19. Or set up a shared calendar, so you know when the other person will be free for a phone call or video chat.
Responses have been edited for length/clarity.