I agree with nuc. Stick to a topic/product/service and use the right keywords. Google can detect improper metatags and will downgrade your site if you get 'keyword verbose'. Google has some great analytical tools including keyword suggestions and keyword rankings.
Backlinks are the single best way to increase traffic. Besides the social networks, you can submit articles with back links to many sites looking for content authors. One place to put your backlinks is in comments you can make on media sites (TV, newspapers, magazines, etc.), just find articles regarding your subject matter, comment and point them to your site for further info. Make sure you are relevant to the thread.
If you are trying to drive traffic to your Hubpages articles, you should know Google allows users to block Hubpages results from searches with a single click. If you have your own site, use Hubpages to backlink to it. Plus, you get 100% of your AdSense, Ebay, and other advertiser revenue from your own site. If you become a recognized expert on your chosen topic, you can even negotiate directly with advertisers for ad placement on your domain.
If you want to analyze results and fine-tune your SEO, there is a reasonably priced ($175) tool used by some professionals, Market Samurai, at www marketsamurai com. They also have some free PDF booklets with great information.