It is the hardest job to fill and to retain a good person. Everyone wants after school care. Be prepared to pay a lot.

offer guaranteed hours and at least 25/hour. i would also round off at 4 hours even a day (that's my minimum). if you come home from work at 5:30, still pay the nanny for the full time. no one wants to cut their day in half to work at 2:30 by committing to come into work for 3.5 hours at $15/hour.

If you can offer $30+ per hour, that will help you.
I'd start looking now on your neighborhood listserve.

We are new to the whole nanny world and are looking for advice. Starting in the Fall, we'd be looking for a part-time nanny from about 2:30-6pm M-F. We live in VA but need someone who can drive and pick up our 2-year old son at his school in DC and drive home to VA and watch him there until we are home from work. How difficult is it to find someone for those hours and who is willing to drive and has good driving record? Any advice on where to look, and when we need to start the search would be appreciated. Thanks!