I typically pay $5 at fiverr and get 300 when I launch a site.... for sites with good content, those 300 are enough to make it start building on it's own. For my crap sites, the number starts slowly descending.
on your site , put the fb like button , promote your page to as many friends as you can and ask them to promote it , also use online services like fansalve to get more likes.
the easiest, but not most effective way, is to buy likes. on sites like freelancer.com you can get targeted ones starting at 30$ per 1000 likes. It all depends on how much likes you are looking for, 200 quality ones or just 100.000 random likes
If feel just by promoting your site with your friends and their friends should get you some good number of likes... its better this way than buying them
Create your page, use the marketing tab to get code to put the google like or other widgets on your site, so that users can do it directly from your site