Many websites have moved from top position recently which means that Google has changed its algorithm

I have done a little analysis and I found the following conclusion:

Backlinks:
Pay special attention when you reciprocate links. Untrusted website can drop you down. You can have as many links as you want pointing to your site but be very careful who you link to.
Avoid link brokers, Automate link exchange, Automate submission and of course link farms

Domain Age
It is a very important issues now. Google is giving a lot of point to establish websites because it is consider to have a trust by Google. The older the domain is the better is rank

Any other aspect please be free to reply. Thanks

Fernando SEO