The forum search engine in some time e no dey give what you dey look for so in most time I dey Google search engine and if I dey find someone from Google about the forum I dey use the format, on the google search box, type the following
Useful information for Nigerian newbies in Bitcointalk.org
and anyone who has written concerning this topic go come out and you go select the one you dey find, although the author name e no dey come out so you go click dem to find the particular one you dey find.
For me, I think the forum search engine can best be used for fine if a thread is already in existence on the forum, why for a broader aspects about how to fine x, y, z about the forum, then Google is a better tool for that, such as; How to post image on Bitcointalk forum & e.t.c
I have used the forum search engine before and I am using Google search engine as well. I prefer Google search engine. If you click on forum search beside home and profile link, the first search engine that it suggested is even Google search, them followed by the forum search.

I prefer to go to google search engine directly and make use of it. But newbies need to be careful and know the risks of using Google search English that can bring up ads which are scam links.
Some people may also prefer to use the forum search which I do kit think is bad either. I have used it before and it works good and accurately.