Im no expert, but just my 2 cents. As a sub I love saying no in a playful, whining, pleading sort of way. So, saying, "no" as a means to an end just wouldnt work for us..to each their own. I do recommend a safeword or as someone else stated some other form of a surefire escape....dropping an object, a hand signal..something.
My only other advice would be this...dont rush and if you decide this is something you would like to delve further into, do so slowly at a comfortable pace. I found myself head over heels fullspeed ahead in the beginning and in rushing to learn or please you lose much of what is important. Good luck in whatever you decide!