There are certain features that are common to all search systems. By identifying these common features, you know what to expect when you search the different systems. That means that the Web sites that match you search terms best should be listed first.
Different systems use different methods to identify which Web sites are most relevant .
Some may even use a combination of these. The search systems frequently do not publish their methods for ranking web sites. However, when searching, if you have looked at the first 20-40 web sites and have not found any appropriate web site, try using different search terms, or try searching in a different search system. Therefore you need to identify any and all terms that you can think of to describe your topic. Remember that anyone can put anything on the Web.