rule number 1: be polite. this is the person who will, potentially, raise your child in your stead. be nice to them. always. give bonuses. give vacation time. say thank you. a lot.
rule number 2: pay appropriately. do some research before you make an offer. find out what the going rate is in your area. ask around. heck, ask the person you're interviewing, they probably know. and remember, you get what you pay for. if you offer someone $9 an hour for childcare, housecleaning, laundry and dishes, you are an idjit.
rule number 3: do reference checks. oh, you're shocked that the nanny you hired for $9 an hour, who you didn't do reference checks on, has a meth problem? don't be. you hired him/her after meeting them on the internet and talking with them for 15 minutes and then you didn't do reference checks. duh.
rule number 4: show respect. your nanny, believe it or not, is not just a meat-suit who shows up every day at 8 am to raise your kids. she/he has a personal life outside of you, with friends, loved ones, hobbies and a plethora of interests outside of your children (though i'm sure your children are lovely). don't pry, but maybe show that you're even a little bit invested in the person who will raise your children for 50 hours a week. create a bond. also, say thank you.
rule number 5: be reasonable. this person, once you hire them, is not in this line of work so that he/she can be at your beckon call every day. this person is doing this work, hopefully, because he/she loves children, is good with children, and finds it rewarding. be home when you say you're going to be home. don't take advantage. and for the love of god. say thank you.
duh.