Trust each other.
This may seem pretty obvious, but for some people, it's easier said than done. If you or your significant other is extremely jealous, a long-distance relationship probably won't work out. Don't get me wrong, I get jealous sometimes. I mean, I'm a girl. But I'm not the type of person who is going to not talk to my boyfriend for a week because he went and had coffee with one of his friends who happens to be a girl. I have a lot of guy friends, and he has a lot of girl friends, but we know where our loyalties lie, and we trust each other enough to know that hanging out with someone of the opposite sex one-on-one doesn't mean the other person is being disloyal.
Talk every day.
Jon and I have a lot of commitments every day. Not just work and school (for him), but also making time to see friends and family, blogging (for me), and whatever else may come up. It's important to set aside time each day to talk to one another. Jon and I usually text throughout the day, but we also make sure we talk on the phone at least once a day (sometimes multiple times if we're lucky). We used to Skype, but my computer is old. He also has an old iPhone, so we can't FaceTime. If you do have these capabilites, I highly recommend using them as often as you can.
Be honest.
This is a huge one for me. I've had friends tell me about things they've done that they've kept from their long-distance girlfriend or boyfriend, and I just don't understand. Jon is my best friend, and I tell him everything. Yes, he gets tired of listening to me, but I still continue to talk. If you feel guilty about something you've done, it's easier to tell your significant other about it rather than having them find out in a different way. It'll come to the surface one way or another, so just be honest about it. Honesty is always the best policy; that's a cliche for a reason.
Surprise each other.
I'm a big believer in sending people things in the mail, especially when they're not expecting it. For Valentine's Day this year, I sent Jon something every day up until Valentine's Day, then I gave him his big gift. Jon uses an app called Postagram that lets you choose a picture and write a message and for a small fee, it send the person a postcard. It also allows you to pop out the picture, but I like to keep it intact. And you don't always have to spend money to do this. You can send them a long and sweet text or email or even a long letter (okay, you have to pay for the stamp, but what's 45 cents, right?). You can also leave a note for your significant other to find later (this is something you'd have to do while you're together). It's just little things like this that will make your significant other know that you're thinking about them.
Plan to see each other.
Being away from each other for a long period of time is hard, but you can make it a little easier by planning when you're going see each other next. Try to make definite plans to see each other while you're together. That way, you'll have something to look forward to when you have to leave each other. Jon and I try to see each other at least once a month. When we're lucky, it'll be more than that. We also already have plans to go on a week-long trip in March, so that's also something we can plan together and look forward to.
When you're together, be together.
When you're talking with you're friends about your significant other, it's easy to say things like "Next time he's in town, you'll have to meet him" or "When she's in town, let's do a double date." That's all fine and dandy if you're going to be seeing each other for an extended period of time, but when it's just a day or even a few days, it's important that you spend time with just each other and try not to involve your friends. You get to see them all the time. They'll be there when your boyfriend/girlfriend leaves. Try to spend time together without outside distractions.
Plan your future.
If you're committed enough to be in a long-distance relationship, hopefully you see your significant other as someone you want to be with long-term. If this is true, then it's important to talk about your futures together and figure out how you will turn your long-distance relationship into possibly living together or getting married. Jon and I are from two different places, and we definitely plan on getting married. I don't want to live in Louisiana, but he's lived here all his life. We still have a lot of things to figure out before we take the steps to get married and settle down.
The success rate for long-distance relationships isn't great, but not all long-distance relationships are doomed to fail. As long as both people in the relationship communicate with each other and make it a point to be a part of each other's lives every day, a long-distance relationship is definitely possible. We've been doing it for over a year now, and we're happy as a clam.

-- tiffanykhyla.