Searching habits and the value of rare words
One of the interesting aspects of working on search relevance is that it really makes you think about how to be succinct and specific in the expression of a concept. Looking at dissatisfaction reports with search engines gives a little insight into the challenges people face every day in expressing what they're looking for.
For example it's tempting -- and very common -- to describe something in general terms with the expectation it'll be easier to find. It definitely easier to find something that way but the chances of it being what you're looking for are generally worse. It's almost always better to think of the most rare characteristic of what you're looking for and search for that instead.
Of course search engines are trying to reduce the frequency with which this happens by relying more heavily on on context, history, and other things, but it never helps to be more specific whenever possible.