It is not usually THAT important to find the queen but on the odd occasion
that it is essential she will know and will hide.  You know this will happen
as you have heard of Murphy's Law.  Take along a spare brood box.  Place it
on a board a few feet away from the hive.  Go through the hive. Take out
frames one by one.  Examine for the queen and place them in the spare box
arranged in pairs with a gap between each pair.  When you have half emptied
the brood box use the space you have created to arrange the remaining frames
in pairs within that box.  Leave the boxes open to the sky. Take a break for
a few minutes for the bees to sort themselves out.  Watch for clues to the
whereabouts of the queen such as fanning.
The queen will shy away from the light and, if she is there, will be in the
dark between two frames.  Take out the frames from the box in pairs and part
them as if opening a book and usually she will then be found fairly easily.
Chris Slade