Know your audience to estimate intent, a bit of advice from Da Vanzo that shouldn't come as a big surprise. He describes a variety of tools that can help you understand a site's demographics and the keywords searched on. Through Google AdWords, you can determine what gets the clicks. He writes that since Google AdWords factors ad click-through rates into calculations, you can presume top advertisers are either getting a decent CTR, or are paying through the nose for clicks.