When you begin the task of acquiring quality and relevant backlinks to your website there are many factors that can increase or decrease your search engine rankings. The page where your link is located should be indexed by Google and the page should also have a Google page rank. Link pages with more than 30 out-going links are less relevant to the search engines. Also look at the Google page rank of the landing page for your link. If the page has a Google page rank this is also a quality backlink. Backlinks to avoid would be a zero page ranked webpage, especially if the home page has a zero page rank. Especially avoid link farms, webpages which contain more than 100 unrelated outgoing links, This type of link page is frowned upon by many major search engines. Also avoid webpages and directories that list their results in alphabetical order, as their database increases your link could be moved to a less relevant page with less pagerank.