You can either trade or purchase back links yourself or get an SEO comapny to work on it for you.
Keep working on building back links and good content for you site. The PR represents how important the site is, but it's not the most important...
I would recommend getting a professional SEO company to advice you and offer some options to increase hits on your site. Building back links will...
I like it, it's very clever!
Anything under 35% is desirable in my opinion. As someone already mentioned, it varies per niche but aim for that level and you won't go far wrong.
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