Recently, I saw that some of my sites jumped incredibly in Google for many keywords.I had no unusual on-page SEO, and not many very great links as well. All I had was very interactive content and site. When users landed on my site, they were clicking links, downloading (legal) files, filling out email opt in boxes etc. I even place videos so they are viewing videos and other media are being thus rewarding my site with high SERPs. So I suggest everyone to make their content long, place relevant internal links, make navigation of site very rich, use media wherever required, and USE GOOGLE ANALYTICS!