When I did this a long time ago, it was difficult to get the information. The reasons were at that time, that the search algorithm is being tweaked for user and

When I did this a long time ago, it was difficult to get the information. The reasons were at that time, that the search algorithm is being tweaked for user and then some SEO jerk comes along and puts his page in front by tricking and optimization. I don't think it has changed much now. But there are plenty of documentation from Google on this - what they want and what you need.