See each other more frequently - pay for both of your flights using a credit card that awards you airmiles.
Choose a card that gives you airmiles for the relevant airlines and allows you to accumulate points quickly. Check out The Telegraph's list of best cards in 2017.
Create a shared calendar.
While you may not be able to attend events together, it is useful to know the schedule of your partner so you're aware when they are free / busy / stressed out / not reachable. This is especially handy if you are both living in different time zones.
Speaking of time zones, have the time of your partner's location on your phone.
It might be obvious, but it will help you to avoid calling just after their lunch break or texting at 5am.
Having a shared, goal-oriented activity can keep you closer. Apps like Strava allow you to track and share your progress, set goals and compete with / shame your partner. If sport is not your thing, you could learn a language via apps such as Duolingo or do a free online course together.
Watch Netflix together.
Netflix is an integral part of any healthy / maturing relationship, and now with the Chrome extension Netflix Party you can watch it together without being in the same country. Just send a link to whatever you're watching and make comments in the chat section.
Postcards from the trip to the museum you just went to, flowers, a book you've just read, a box of creature comforts. Receiving physical objects from your loved one will help take the relationship out of the sterile digital space back into the real world.
Have your next trip planned.
This way you'll both have something to look forward to and there won't be any ambiguity on how long you'll be apart.
What are your tips? Let us know and we'll add it to the list!