We didn't waste any time when we were physically together
When I visited my girlfriend after weeks or even months of being apart, we didn’t go on bar crawls, go to concerts, schedule ski trips, or whatever else people do when friends are visiting. We spent our time working on our romantic relationship. I'm not just talking about sex; romance, cuddling, and intimacy are all just as vital to a healthy relationship. We took advantage of being together whenever we had the chance.
At the very least, we found it's good to make sure you and your partner can enjoy each other in total comfort when you finally see each other. Whether a relationship is long distance or involves a shared bed, bathroom, and Netflix queue, the same components have to be in place for it to work — communication, patience, affection, and trust.
We kept a close eye on our travel expenses
While we were in college, my wife and I knew we would always be near enough to drive to each other around the holidays and summer vacations at home since we grew up in New York and Washington, DC, respectively. We always planned car trips during these periods, but during the gaps when we were at school or traveling, we would trawl the web for cheap flights.
Travel isn't cheap these days, and that's especially true if you and your partner live far enough apart that flights are the only logical way to meet up. As often as possible, we planned our visits in advance and were flexible with the dates. We even set up flight alerts for low-cost travel options in hopes of finding reasonable flights. Just because you and your SO are deeply in love and committed and such, doesn't mean you need to spend a small fortune to be together.
We gave each other space, even when we were already miles away
When I was in Europe for a semester, my wife and I had one weekly planned phone call where she would wake up in the middle of the night on a Tuesday to talk to me and I would call her from the landline at a cafe I worked at. I also called her from random payphones, emailed regularly and always shared when I would be traveling to other countries, but aside from that, it was understood that for days at a time we'd simply be out of touch.
In any relationship, you're always working to be closer, but that doesn't mean you have to be in lockstep with every single aspect of everything. Don't expect to be fully a part of each other's lives until you live together. Your long-distance partner is going to have friends you don't know well, will go out to bars, movies, and more without you, and will generally live a rather large part of their life separately from you. And in some ways, that is liberating.
We planned for our future
My wife and I were engaged for the last year and a half of our time apart, and were actively planning a wedding for much of that (more credit goes to her on that, of course). We were also scoping out apartments in LA, planning a honeymoon, looking for jobs, and generally, y'know, planning our lives together, with that last word being the operative.
The long and short of a long distance relationship is that if you want to be together, you should be planning for and working toward the soonest possible time when that can happen. Instead of fretting over travel arrangements and aligning your calendars indefinitely, start thinking about definite steps that will bring your long distance relationship to an end and start the next phase of your romance — a regular in-person relationship.