Searching the wiki
Searching the wiki is easy. Enter a search term in the box above, or you can use the little box on top right while you're anywhere on the wiki.
Special:Search is the 'advanced' search screen. You can get to it by clicking the search icon without entering a search term. It gives you a few more options to restrict your search to different namespaces. Tick the boxes for namespaces you wish to search. If you want a different default setting for these, go to Special:Preferences and the 'Search' tab. Note: Searching all namespaces might be the most logical thing to do. In fact the latest versions of MediaWiki have that as the default.
The wiki is divided into namespaces. Most content is on the 'Main' namespace, although there's a fair amount of wiki discussion taking place in the 'Talk' namespace. Note that this is not the same thing as the 'talk' mailing list (see below)
The wiki has namespaces for some languages, which means you can now search only the german language pages by ticking the DE namespace for example.
If your search term is hitting upon an exact page name match, but you wanted a search, then you can select from the drop down which appears while you are type. Select "contain x..." at the bottom. Alternatively enter the advanced search screen rather than using the little search box.
You might prefer to use google, since it sometimes indexes stuff better than the wiki search mechanism (although it's not quite as current) More importantly...
The custom google search set-up at a http://bit.ly/osmsearch will google the wiki, mailing lists and forum all at once. There is a treasure trove of information buried in discussions on our Mailing lists.
If you do find some useful information which is not in the wiki, it probably should be added somewhere. You could add it! Editing the wiki is easy!