Ask HN: How to advertise online

I want to learn all there is to learn about what the most effective ways to advertise online are. - What advice do you have? - What books should I read? - What articles would you recommend? Specifically, I'm starting a website that has better student reviews of colleges. I need kids to answer the questions about their college, and I'll pay them 5/10 dollars. I just need to advertise this offer to them. I was thinking that advertising on subreddits would be effective, but I need to explore my options before trying that. See http://www.collegeanswerz.com/ for more information.