Long distance relationships are intended to be temporary. In other words the couple hopes and wants to be together permanently. They are only apart due to circumstances (college, military, career...etc) Eventually one person will have to relocate at some point for the relationship to succeed. If the time frame for this has not be discussed then the relationship is NOT all that serious.
Today there are numerous ways to stay in contact via webcam, Skype, phone, text, email, as well as sending traditional letters and cards. It also helps if both people have the means to visit one another periodically. Before we got married my wife and I took turns flying back and forth to have a 4 day weekend (each month). This lasted for close to a year until I relocated to live with her. All along we had the mindset that our long distance relationship was not a permanent situation.
The biggest challenge for any long distance relationship is how each person deals with loneliness as well as making up after disagreements. One of the reasons many long distance relationships fail is because they don't have the means to see each other enough.
This is all too common when couples are at seperate colleges. There are many social activities and parties on a big campus. Very few 18 and 19 year olds are going to lock themself in their dorm room. Socialization leads to friendship and friendship sometimes leads to relationship. Simply put they don't have the maturity to tune out their surroundings or avoid temptation at that age. Being young means exploring and finding one's self.
As for arugments and disagreements... It's kind of tough to make up by phone, email, or text. You can't seal it with a kiss or a hug. On the other hand it is easy to ignore or be ignored in a long distance relationship if your mate is angry with you. Sometimes if there has been a major fight one person will have to make an emergency visit to patch things up or else the relationship is in danger of falling apart. Best of luck!