I would have to say Stephen really gave good advice on that. I have never been in a real long distance relationship so my advice would be rather noobish. I will say that honestly is always the key to any long lasting relationship.
Honesty, and openness are 2 seriously important factors in any relationship. In a long distance relationship (which I am in), you should also have a LOT of trust for the other person, and never put too much pressure on them.
Also, along with that, you should always try to meet up as often as you can. Communication, and mutual respect/love is one thing, but NOTHING can replace the feeling of holding your partner, or being next to them. Yes, leaving them again will hurt, but...that will make you stronger