In-House Referrals Are #1

http://www.glassdoor.com/blog/foot-door/

Nearly a quarter of all new hires come from referrals offered by those already working for a company. New hires do come from other resources--job boards, college recruiting events, career fairs and social media, but in lower percentages. See the full chart at the link above.

So how should you approach the job search? Networking those who already work at companies where you would like to work. There's a detailed explanation here about how to do it with a light, deft touch that doesn't come across as pushy.