I remember a study that if long-distance relationship last past the first few months (which they do less often than face to face relationship) they last longer and are more committed than face to face relationships.
In other words, LDRs tend to fail early or last long, with less middle ground than non-LDRs.
Anyways. I've never had a successful relationship that wasn't an LDR, so obviously your milleage may vary. How far apart are you? And is it the same country? France vs Spain might be much closer than California vs New York, but at least in the same country you don't have to worry about visas and immigration and so on.
My advice: talk on skype or the phone often (if your plan is good for that). Write letters every so often and send each other stuff because it's good to have something you can actually hold and look at. Have some small thing of each other you can wear, like a ring or a bracelet or something, so you feel together even when you're apart. Be very aware of each other's schedules and of the time difference, if any, and try and have some routine, as stability gives you some safety, which you otherwise don't get in an LDR as you don't know where the other person is, what they're doing, you can't just drop by, etc.
Try having dates. Get the same movie and watch it at the same time while on skype. Cook while on camera, do your laundry while on camera. Not all the time I mean, but on your date day, just spend time together but still live your regular lives too and watch each other do so. Things like seeing each other cook and do laundry make you feel closer to one another.
If you can set it up so you both have laptops with skype, for instance, and you put them on your bed and fall asleep together, it can be very bonding. Of course not everyone can sleep right next to a computer and with some lights on (so you can see each other).
Tell each other about your day a lot. You'll already feel excluded by not being there, you want to feel part of each other's lives in some ways at least.
And that's about it for now. Good luck with everything.
EDIT: I almost forgot. LDRs rarely work if there is no end in sight, unless you're both perfectly content never meeting, which is rare. So you need to feel like it's going to work in the long run, and have a plan, especially if you live in different countries. Who's going to move to whom? Are you going to both move to a totally new place?
You don't have to decide right away, you can experiment first of course. Also, try and see each other as often as possible in person. You might be able to once a month, once every three months, once a year... less than that probably isn't very viable unless it's a single time apart. Also try not to go too fast until you meet for the first time if that hasn't happened yet. Lots of things are different in person. You get to smell each other, feel each other, taste each other, and the two senses you can have from a distance (sight and hearing) can be different (they might look different, they might sound different).
Making the transition can be painless or heartbreaking. It depends. You might fall madly in love with someone who isn't who they are when not online. And then it might not work out, because when talking online you'd wish "they" were here, but if face to face you'd still miss them, because they're not the person you love and want to be around.
So I recommend seeing each other for the first time as early as possible, even if for just a very brief amount of time, just so you can know each other that way. Then you can work on moving closer together, etc, and having longer periods of times away from each other is less big of a deal because you know what to expect more.
