Not sure why I'm just now writing this, but these are my thoughts.
Sub and Dom:
Set personal goals for yourself. Ask your Dominant to help. Do it together.
Set expectations for your dynamic and hold each other to them. When you say you're going to do something, do it.
Mistakes happen, but saying you're sorry only really means something the first time. After that it's meaningless.
When you don't understand something, ask for clarity. Misunderstandings cause chaos.
Be honest and don't take advantage of what is being offered. Some of us have big hearts and others take without giving.
This arrangement is sometimes only BDSM and sometimes it includes more of a relationship. That wording is iffy, sorry. Make sure you both have a clear direction. Half falling in love, is also half not. It sucks and hurts like hell, so be clear.
LDR in this world is not easy and it's not for everyone. You have a commitment, yet are physically alone. Give it your best, give everyday your all. It's OK if it's not for you.
Lastly, be true to yourself and your needs. You deserve the very best possible in life. Believe it, live it.