One of my biggest beefs with how people search for information is that they don't know (and don't care to know) how the tool that they are using works. Whenever I bring this up, the common response is something like, "You don't have to be an auto mechanic to drive." But I think this is a misunderstanding of what it is to know how something works.
To drive, you certainly don't need to know about everything that's under the hood, how spark plugs ignite fuel causing pistons to move up and all the rest. It may help in some way, in order to push your car to its extreme, or to ensure that you are not causing unnecessary harm to the engine, or even how to interpret subtle reactions the car may have to what you're doing. But you DO need to know what happens when you turn the steering wheel, when you step on the accelerator, when you turn the key... You need to know what the result is in pretty good detail (how much do you turn the steering to cause so much turn in the front wheels or how much gas to give it to accelerate a certain amount). You don't need to know how the car does what it does but you do need to know what it does. That's what "knowing how a car works" in a operational manner means.
Similarly when searching for information, you need to know how your search tool works. You don't need to know Google's proprietary code underneath the "hood" or what programming language PubMed uses on it's servers. You do need to know that when you type in a word in the Google search box, it's looking for entries in its database (i.e. web pages) that has that word in the web page (or rather Google's record of the web page) somewhere. You need to know that PubMed not only finds the article citations that has the word that you typed in somewhere but also maps that word to possible subject labels and includes the articles tagged with those too.
But too often, novice users merely type words and phrases into the box without considering what the box will do with those words and phrases. Some think they are clever and include Boolean terms like AND or OR or short forms of those like the plus (+) sign, but don't think to check whether the tool recognizes those terms or whether it uses them in the way they think. And I've come across a few tools that don't know themselves how they work. (For example, TRIP at http://www.tripdatabase.com claims in the search tips that users can include the connector AND but it "ands" terms by default anyway, making using the word useless.)
So, please, when you're searching, test out the tool a little first. See what changing your search a little will do to see if it does what you think it does. If you think adding more words will get you closer to what you want, see if adding any other word actually reduces your results. If it increases them, it's not doing what you think. So test drive your search engine or article index a little first. Or better yet, ask a librarian.