Relevant linking is the key. You want to link to sites that have the same content or related content of your site. You want to link with sites that have the same PR as yours or better. Remember too, that everytime Google does the "Dance", PR of sites will change also.
Optimize your site for the engines. There's plenty of articles and tutorials around to guide you, or you can hire out to get the job done. Research and read up on SEO before you do it yourself or hire out.
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