For licensed electricians I've had good success from advertising in our area's largest newspaper, the Boston Globe.  Many responses.  I tried 4-5 smaller, more local papers with poor results.  Ads are expensive, but at least you get what you pay for.  When I thought about it, if I were looking for a job, the Globe is where I'd look too.
I've had a lot of success hiring apprentices from other trades.  I have 3 excellent apprentices who formerly worked for a HVAC company.  Good people, excellent mechanical skills, just needed to learn electrical.  Working under a good licensed electrician, they progressed extremely quickly, and one has since become licensed.  One contacted me, and the others followed his footsteps a year later.