Search engines view links as votes for your site but also understand that not all links have equal value. A link from a top ranked web site for example would carry more weight than a link from a site ranked 1 million. The process of determining the quality of links is a very complex one. Here are a few things a search engine may look at:

The relevancy of the site linking to your site

Logic says that if you have an excellent site about bicycles, other sites within the bicycle industry would link to you. This is the exact reason you should never be afraid to ask for a link from a competitor. If the competitor is any good they will know the importance of links, if not, you can explain it to them.

Always remember that you want to get as many links from within your industry as possible in order to establish a solid foundation. You can furthermore not really be penalised for incoming links. Links from other industries will simply carry less weight or in the worst case have a weight of zero.

The PR value of the page linking to your site.

The PR score of a page linking to you IS important, the higher the better. This however does not carry as much weight by itself as it once did. Simply download the Google Toolbar to view the PR of any site. This provides a good yardstick for the sites value. You must however also keep the items below in mind and not only base the power of a link on its PR value. 

The frequency at which links are added/edited/deleted on the page linking to your site.

A search engine may monitor how a site uses its linking power. What this means is they will keep track of how many new links are added, the frequency at which they are added and how often they are deleted or replaced. They do this in order to get a better idea of a sites link stability. This helps determine if a site is actually a "good site" or one that is merely selling links. Sites that sell links will logically be more active in the add/edit/delete categories.

Search engines give more value to old links that have "aged" than to new fresh ones. Links that you have had to your site for 2 years would logically be more valuable than ones you have had for 1 week. This is why new links are put in a "sandbox" and not fully counted for 6-9 months. Keep this in mind if you ever wish to purchase links, you will need to commit to at least 1 year. 

The IP address of the site linking to your site

Location of a link is important. A site that is linked to "naturally" will have links from all over the net. They will not only have links from sites on the same "address" as them. That does not seem natural. How can a site only have links from one place and expect to be truly popular? To win an "election" you need links or votes from all over.

Another reason the IP address is important is due to the fact that webmasters would build huge networks of interlinked sites.

Use the C-Class checker tool to find out the exact location of anyone you wish to trade links with. This of course does not mean turn down links from similar locations, just try keep it all natural.

The ownership details of the site linking to your site

Again in order to combat link networks search engines may look at the "whois" info of a site. This way they can determine if several different people are linking to a site, or if it's all the same person. Should you wish to view the "whois" info for any site simply visit www.whois.sc

Should a top ranking site develop "organically" logic tells us it would have many links from several different sites each with different owners.

3. Where to Purchase Links

Remember when purchasing to links to do so from relevant sites - sites in a similar industry to your own.

Below are two excellent sites you should visit:

www.linkadage.com

www.text-link-ads.com

4. Where to Purchase Traffic

Purchasing traffic has several advantages if done correctly. Always remember to track the campaign performance in order to monitor the Return On Investment.

Below are three excellent sites you should visit:

adwords.google.com                  Google Adwords

www.overture.com                      Yahoo Listings

www.msn.com                           Microsoft Listings

www.metricsdirect.com              Metrics Direct

Source: StartRanking.com