When you first enter the more public BDSM community one of the largest catch phrases you will here is SSC, also known as Safe, Sane and Consensual. It is a security blanket approach to safety when playing and negotiation of play. As a submissive, you have a lot of responsibility to keep yourself safe and well.
When I first learned about SSC I found that it was very important that I understand what it means to me and my experiences in BDSM. Everywhere I went I found essays that mostly pertained to playing safely, negotiating and choosing the right partners. It didn't really sit well with me because I was looking for a relationship and not just play. So I defined it for what I was looking for.
While most essays you read will undoubtedly say that you need to play safely with respects to using barriers, who you play with and to your knowledge level or experience level none of them touch on relationship safety.
Safety as far as relationships go would be protecting what you feel to be valuable. This would be your limits, your needs and wants and any other substantial belief systems you already have in place, such as religion or family ties.
You also want to protect your physical and emotional safety. During negotiations for a relationship, or just getting to know one another, figure out how your partner plans to take care of you and if they will allow you some leeway in how you can care for yourself if needed. Even slaves have a responsibility to make sure that their emotional and physical well-being is taken care of.
For sanity, the essays out there stick with knowing fantasy from reality and not acting on fantasy. There is so much more attached to the word sane though. For example, what about expectations of service; keep them realistic. No submissive should be expected to learn 4 pages of rules and protocol in a short period of time or kneel for hours on end without a break. This is what fantasy porn is made of.
Also, listen to your gut about red flags and uneasiness. You generally don't have invalid feelings when you feel it in your gut. If something feels crazy, then it's perfectly okay to investigate it. Keep it yourself sane.
Of course, the two or more parties involved should agree to the play activities, it's pretty much a given. BDSM isn't about forcing the unwilling at all. But also, this part of SSC covers illegal activities such as incest, child abuse, animal abuse and other unsavory activities.
When relating it to relationships consensual should be that all relationship items should be agreed upon. There are good dominants and bad dominants. Holding onto your wits and enforcing your rights should keep the bad ones at bay. This means that no rules should be forced upon you that you don't want to do.
All in all, keep it safe, sane and consensual.
In another essay, I'll talk about the alternative to SSC called RACK.