Search phrase length shouldn't be more than 100 characters. Words having less than 3 characters, will be ignored, except for the "Whole phrase" type search, when they may be searched alltogether. For better search, find the one most important keyword in your search term, and try to search by it first in topic titles, then in message bodies. Analyzing results, you most probably will find what you are looking for. If you specify a larger number of search words, your search will take longer and the results may be less specific. In the result list, most recent messages are shown first.