Dearest new Domme, the most important thing I can stress is that you MUST talk with your subbmisive. In order to please her, you have to know what she likes and does not like. Have you and the person you are going to top been together a while, and you are just adding this lifestyle to your own, or is this a new relationship?
If you and your sub have been together or have known eachother a while, then you might allready have some idea as to what she likes and does not like. If this is someone new, I will greatly sugest using the checklist that MG linked above so that you and your new submissive have a starting point.
For play ideas, try joining and looking around the Acadamy here, or come into the chat and just watch a few seans that people get into. Not that I am saying that is all we do in the chat, but it is part of it, and I for one have gotten more than one idea from just watching others sean.