It really depends on the content of your site and your goals. Are we talking about a personal blog, e-commerce site, affiliate marketing landing page? You have the whole spectrum from just writing good content to Black Hat SEO. Hell yesterday I found someone selling 10,000 unique hits. I guess another thing to think about is, what purpose does your traffic serve? All you looking for huge numbers of visitors so that you can justify selling ad space or do you need conversions for PPA or PPC campaigns?