What are the effective ways to improve keyword ranking?

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The backlink reporting tool opensiteexplorer.org reports you have 14 links from 6 sites (they can overlook low quality link sources), you certainly an benofit from more backlinks, with perhaps 1/3 of them including keyword variations in the anchor text (the blue underlined text that one clicks)

Don't repeat packagingsuppliesbymail in every backlink make a natural looking variety, packing by mail, shipping supplies, etc.

Here's a Search Engine Optimization primer by an SEO authority, too much of the stuff taught by others is out of date or simply inaccurate.
http://www.seomoz.org/beginners-guide-to-seo