Two links so as not to repeat the essays in this thread.
Choosing a Master/Mistress: Lessons from a Pet Mistress
http://www.bdsmlibrary.com/forums/showthread.php?t=3737
"The Acid Test, it might just save you."
http://www.bdsmlibrary.com/forums/showthread.php?t=3647
Whether you are in a relationship or selecting a partner, both authors have some excellent warning signs and safety tips that are worth a read.