great guality content + More Traffic = $$ You shoud achieve this equation. You can get more traffic by building more backlinks
You have to attract search engine traffic (via SEO) and with correct blending technique, you will be seeing your fat check every month Another great technique I have is the Exit Page Strategy.
I'm not an expert. Just from my short experience. (1) Find the right niche that pays relatively well. (2) Build your site SEO friendly (3) Bring traffic, not neccesary huge (4) Have HUGE patience. Don't give up if during the first 6 months you don't earn but pennies. This (i think) is the common mistake people do. (5) Have a website that is usefull to visitors and update it monthly (or in shorter periods if you can) (6) Don't spend time to bring fake traffic (7) Start more than one website Good luck !