1. Number of backlinks
Number of links to a website pointed to is a extremely important ranking factor. If you have many links pointed to your website it means that your site is important and provides valuable information.
The more links you have pointed to your website,the more chances ar for you to be on tot of search engines position.
2. Relevance of links
This factor is closely linked to that described above. He refers to how relevant are the links that your website receives.
Quite many webmasters are able to produce a large amount of links in a relatively short time. That don't means that they will be able to "climb" a site on the first page (although it is quite possible for keywords with low competition). Created links must be relevant to the site pointed so that search engines give it "weight".
This factor has two aspects: anchor link and how relevant is the site that sends the link.
An html link is presented as anchor.
A link that will serve as key word will be granted more valuable than a link using the anchor terms like "click here" or "Home".
Note: use combinations of key word when you will create the link. Using the same anchor format in most cases can result penalties because it will be see as an attempt to manipulate the results (aka Google Bombing).
A link takes on even greater importance if it comes from a site that is to relevant to the keyword / topic chosen.
Example: You have a car forum.If you will recive a link from an auto website it will be more valuable that a link from a fishing site because it is not relevant to your subject.
3. Age of website
This factor is very important and unfortunately can not be controlled by the webmaster. Google apply an "aging filter" known as the sandbox.
New sites will have a good ranking in the first 2-3 weeks after that will be sent to the "sandbox". They will not be class competitive keywords for a period between 3 and 12 months. The more your keyword important the more you will stay in sandbox.
This algorithm has been implemented to prevent spam , to separate the valuable website from the one wich use aggresive link building campaigns.
4. Number of new links
This is another important factor in terms of ranking a site. All too many incoming links in a very short time can be beneficial but also can and damage.
A site that receives a lot of natural links (they are not created by the webmaster) can reach the first position because it is considered as "hot news". If the rate of increase of the number of links is constant ,chances to reach the first position are big.
At the same time the increasing of link can damage your webste if the link a poor quality or if they ar coming from spam sites.