You'll want to advertise on care.com, neighborhood list serves and ask neighbors. Things you can do to improve your odds of finding someone include guaranteed pay even if you don't need the a particular day or week, include dinner so it's not 7/7:30 when they can finally eat, be open to older high school girls, be open to one person on mwf and another on t-th (or whatever), competitive pay, not the bare minimum you think you can get by with, good communication and clear expectations. Make sure each party is on the same page.