QESTonline:Searching
A lot of this information is taken from the MediaWiki User's guide, to check out the full thing go to [1]
Avoid short and common words
This is the most likely cause of an unexpected failed search. If your search terms include a common "stop word" (such as "the", "one", "your", "more", "right", "while", "when", "who", "which", "such", "every", "about", "onto"), then your search will fail without any results. Short numbers, and words that appear in half of all pages, will also not be found. In this case, drop those words and rerun the search.
A lot of common words are disallowed as search terms, for a full list see [2].
Words of 3 letters or less by themselves will also not yield any results (no luck searching on "SQL" then).
Words with special characters
In a search for a word with a diaeresis, such as Sint Odiliënberg, it depends whether this ë is stored as one character or as "ë". In the first case one can simply search for Odilienberg (or Odiliënberg); in the second case it can only be found by searching for Odili, euml and/or nberg. This is actually a bug that should be fixed -- the entities should be folded into their raw character equivalents so all searches on them are equivalent.
Phrase
There is no method for searching for a phrase. Contrary to what you might expect, enclosing phrases in double quotation marks such as "can of tuna" will retrieve all pages containing "of" "tuna" and "can".
No regular expressions or wildcards
This is somewhat dissapointing but you cannot use regular expressions or wildcards such as ? or *. If you don't know what that is, don't worry about it. To search for pages with the words "boat" or "boats" search like this: "boat or boats".