I have been trying to field the wonderful world of internet porn trying to find information on understanding the deeper levels of submission in a sense of comparing the difference between submissive and slave. I haven't been too successful on the information gathering so please forgive me if this question is sounds a bit naive, but i have a questions on when that level of submission goes deep enough to the point that the need to fallow goes beyond ones personal limits, when the need to please goes beyond a sense of self preservation and voice of reason, when the need to please out shines the gift of choice?
My first question?
What advice would you give to a sub/slave when seeking out a Sir/Master?

As i have already stated? i haven't been too successful on finding information so with my limited understanding i now am a little confused between the two, submissive and slave. Please don't take offense to my wording and correct me if i am wrong here, but aside from the more obvious 24/7 versus negotiated times, is there more that differentiate between the two? And if there is a line, is there a gray area where one can be both?

Also, in passing i have been told that in these deeper levels of submission that it is important to find a Sir/Master that not only can control the sub/slave but also can control Him/Herself to best avoid the temptation of unnecessary cruelty. Now, i understand the 'temptation of unnecessary cruelty', I'm not so sure about understanding the 'control Him/Herself' part. How does one know how to judge how much control one has during introductions and negotiations? Or is it pretty much a crap shoot and hope for the best?