The search functionality of vBulletin isn’t officially documented anywhere and there are a few pitfalls which make it easy to get useless results.
Performing a search without making any changes will give you a set of all threads that contain any one of the words in the keyword box. Many threads are several pages long and these search results contain no hint of the page or post to find the search result on. With a few simple changes, the results can be very specific and useful.
To get good search results, start by formatting the keyword search correctly.
Phrases:
Enclose multiple words in a pair of quotes to search for that exact string of text.
Example
searching for "gps turns off" with quotes returns only 13 results (at time of writing) while gps turns off without quotes maxes out at 500 results.
Be aware, only results with an exact match will return. In this example, the phrase "gps turns itself off" will NOT match.
Wildcards:
The asterisk '*' can be used at the end of a word in case the word could end with multiple spellings.
Example
searching for reset* will return posts including the words: reset, resets, resetting, etc.
Note: The Question Mark '?', another common wildcard, is not supported
Excludes (NOT):
Specify words that you know should not be related to your search by preceding them with the word NOT
Example
searching for gps NOT tomtom will show all posts that include the word gps, but ignore any post with the word tomtom.
Boolean Operators (AND / OR):
Force specific words to exist without them being in any order with the use of AND, or force one of a few words to exist with OR.
Example
searching for gps AND turns AND off will return any post with all 3 words, no matter their order or placement. Searching for gps OR turns OR off will return any post with 1 or more of those words.
Note: By default, typing multiple words in without any surrounding quotes, or any operators will be treated as if each word is used with OR. In the example, gps OR turns OR off would be treated the same as searching for gps turns off.
Tip #1: Search for Posts instead of Threads (default is set to threads)
Change the Show Results as value from Threads to Posts. The search results will include the exact post instead of just the thread containing the result. Be aware, in this mode the results will be shown with the Date first, Thread Title in bold, Author, and then a link to the individual post printed in italics (right above the first few lines of the post). In most cases, you’ll want that italic link instead of the bolded link above it.
Tip #2: Search Only in Relevant Forums
Many problems, especially related to hardware, will be limited to just your model of phone. Try searching only in the groups associated with that phone to get a more targeted set of results. If you don’t get any useful hits, you can always try a wider search. Hold down the Ctrl (or Command) key while clicking on a group name to pick multiple specific groups.
Tip #3: Sort the results
If you stand to get several hits, try sorting them to get something useful in the first page. Recommended, sort by either Forum or by Last Posting Date. The Boolean operator AND does not function correctly while sorting by Relevancy (See Bug Notes Below).
Final Tip: Save your search preferences
At the bottom, just above the “Search Tag Cloud” is a drop down with the option to save or clear search preferences and a ‘Go’ button. Once you’ve found a good set of search settings, save your preferences now so you won’t have to worry about setting them each time in the future.
Keywords with 3 letters or less will frequently not work because the search function assumes that too many results will be returned. This will cause problems with common searches like 'GPS' or 'ROM'. The only good workaround is to use at least one keyword of at least 4 letters in length. As long as one keyword is long enough, the keywords that are too short will also be considered valid. For example, entering gps off will fail to return results while gps turns will be valid.
There is unexpected behavior in the way that sorting by Relevancy and using AND operators will work. vBulletin performs any search sorted by Relevancy by turning the AND into an OR. This is documented on line 759 of the search.php page in vBulletin version 3.7.4, therefore it is not technically a bug, but seen as intentional (despite being mind-boggling stupid).
XDA-Developers