Facebook now has a system whereby you can pay for an advrtisement for your page to be shown to a targeted audience. There is no way I would ever normally do this but now when you go above 50 'likes' you are given a $30 voucher to try it out.
So I set up an advert to run for 3 days at $10 per day and wouldn't you know I have had about 120 new likes in that period! I can't say for sure that it is the advertisement alone that is responsible but it certainly is the major contributor.
Just thought I would share in case anyone is interested.
Rachael