You interview them and make sure they meet your criteria. I'd recommend a well educated Filipina. They aspire to the same standards as you, are hard working and generally have good morals driven by Catholicism. We were recommended a Sri Lankan when we first arrived, lovely girl, lazy and came with man troubles a common issue, she lasted about 4 months.
We have awlays paid over the odds and ensured the people we employed were suitable. We know others that try to do it on the cheap and are astounded at the lack of loyalty and laziness of their maids. They hire Sri Lankan's with poor English and are surprised to discover the affect it has on their kids. It's not about nationality but capability and in my experience there are far better educated Filipinas available. Interview and then remember you get what you pay for; after all they are going to look after probably your most prized assets so you want them to be happy in their role. They will cost you about 40k/year all up which sounds a lot but for full time child care, I think not.