I second what Sir Russell has said. I have an enormous amount of respect for the man. He's been involved with the lifestyle for probably more years than he cares to admit and wasn't voted "Most Knowledgeable" for his obvious good looks.
Always be safe, sane and consensual. Know your limits and if you are going to stretch them your Dom needs to be watching very carefully and most of all you need to let him know as best you are able where you are really at in terms of pain threshhold.
Good luck and above all enjoy, have fun and lots of orgasms. *smile*.