I know that sounds simple, but please at least look through the library for safety tips. http://forum.literotica.com/showthread.php?t=266656
Make sure she has a safe signal so she can communicate that she needs to stop. Remember that duct tape can damage skin. Have safety shears available so you can cut her out in an emergency. And please be aware that bondage can cause nerve and circulation damage. I've never used duct tape for bondage, so my suggestions are merely a general precaution. Stay safe.
Edited to add this link. There was a good suggestion to put plastic wrap down wherever you're using the duct tape to protect the skin.
Hm interesting. The handcuffs are still in the mail