For concept-based searches, results are best when you enter a lot of words, all of which roughly refer to the same concept. This holds true, of course, only where the 'find any' syntax is in operation. SEE Evaluation of Search Engines - Retrieval Performance Use results ranking criteria where available. However, evaluate usefulness by description. The search engines' algorithms for relevance ranking are most often based on word frequency, word positioning, word weighting.
Search engines are, unfortunately, liable to return such with no obvious reason for doing so.
Don't look too far down the list of retrieved titles. Revise search as necessary, rerunning the query several times, adding further refinements each time. Utilize more than one search tool. Remember, no search engine indexes the whole web, nor do they all index the same sites. Moving to another search engine sooner rather than later can be a more efficient use of time when success is proving evasive.