Use + and - to control the search.

Words preceded by + are mandatory; only pages including those terms will be returned.

Words preceded by - are forbidden; no page including those terms will be returned.

All other search terms contribute to relevance, with pages having more of them being returned first.

+a -b c d e f

means that every result must include a, may never include b, and should include as many of c, d, e, and f as possible.

Quotes are ignored. A quoted phrase is treated as individual words. (Sorry, the engine I'm using isn't that sophisticated. If you need such a search, use Google.)

Searches are handled through a database and thus will be extremely rapid. The database is updated every morning, and doesn't include posts made on that day after the update.

This doesn't understand "plain language queries". If you enter "Will we win the war?" it will search for entries having those five words, not necessarily contiguously, which probably isn't what you want.