We got a nanny through "nanniesRus"
They sent over several ladies for us to interview and we found a fantastic nanny for our boys. We never had to tell her anything. After one week she was running the house like she'd been there forever. Was great with the kids and she would even shovel the drive some days. I miss her
The nanny we have now is related to our past nanny and we brought her here from the Phillipines. She's great with the kids but not nearly as good with the house. All in all having a nanny (live-in) has been really good for us. My brother in law was not so lucky. They did a phone interview and ended up with a girl who was only interested in gaining citizenship. They got a nanny cam and she was fired within two weeks.
I would definately recommend going through an agency and doing an interview at your house so you can see how the nanny is with your kids and her general personality.
If you have any questions let me know.