Back linking - who can be good link partners?

Certain things to consider when you back link:

• The site to which you are linking should be a site with a similar theme. For e.g. if you are a bankruptcy lawyer, you may link to an attorney/CPA website but linking to a jewellery website for instance is not very valuable. This is based on the ranking results we have seen linking with websites in similar industry. When Google crawls your site, it figures out your site theme/industry and values other links in similar industry that back link to you if they are credible. This is purely based on experience & results that we have seen.
• When you decide to link to a website, check the website out for its content, layout, quality manually. Things like too many Ads on the site or junky content or too many outgoing links from the site may be red signals to consider.
• Page Rank(PR) is considered an important factor (though not necessary) to back link. Websites with a good PR are most likely good link partners but always good to check them out.
• Finally a lot of companies out there give you 1000 links for $20 etc. These are most likely junky offers which will not benefit you much. After working for link building of our client sites, I can easily realize that any such offer cannot be feasible cost wise.

Back linking is a full time job which involves manual reviews of sites you want to link to. And equally important you have to keep up your site's position, content, quality etc. good on search engines for others to be interested to back link with you.

That should give you a fair idea. Good luck!