Safe words!!! Always make sure to have one in place. Part of the joy is letting go, from both the Dom's and the sub's perspective. Knowing that your partner wants it and you can give it to her is special, but as you've already realized, your most important responsibility is her safety. The safe word is a way out for her..when you hear it, the activity stops. Its very important to take the time to discuss the session afterward. What did she like, what she didnt like. It doesnt all have to be done in a single session. Hopefully, you have found a partner that you'll get to continue to explore with for years to come.

Ease her into to it. Learn what her desires and limits are. Use that god given gift of 'common sense'. Recognize what types of toys/tools you are using and the potential that they have. For example, a bullwhip in the hands of a novice (like myself) can be dangerous to your subbie. I have no experience with one and am very hesitant to use one on my subbie. They require a delicate touch and a 'properly executed lash' can cause signifigant damage. Whelps and bruising go away. Cuts are abit more serious. You dont wanna break your subbie, they are too rare and special . For myself, I always 'test' a tool on myself before using it on my sub. This way, i know what it feels like, how much strength is required to get a good effect, how much is too much, and she's not as much of a guinnie pig.

There's many more experienced Doms here than myself, so hopefully they will provide better insight than i have. Hope this helps.