Before telling the nanny you are considering about what you are looking for, ask them what they believe are the most important elements in raising a child. It's likely that they will be able to tell you what their honest opinions are. If these don't match your own needs, are they the right person for the job?
Finding a nanny means talking and interviewing several people. This can be a long process. If you have the time, hire a person to do the preliminary interviews for you, even a family member. This can lower the number down to just a couple that are the best for you to choose from.