Man-notify-method

Man-notify-method is a variable defined in `man.el'.
Its value is

friendly

Documentation:
Selects the behavior when manpage is ready.
This variable may have one of the following values, where (sf) means
that the frames are switched, so the manpage is displayed in the frame
where the man command was called from:

newframe -- put the manpage in its own frame (see `Man-frame-parameters')
pushy -- make the manpage the current buffer in the current window
bully -- make the manpage the current buffer and only window (sf)
aggressive -- make the manpage the current buffer in the other window (sf)
friendly -- display manpage in the other window but don't make current (sf)
polite -- don't display manpage, but prints message and beep when ready
quiet -- like `polite', but don't beep
meek -- make no indication that the manpage is ready

Any other value of `Man-notify-method' is equivalent to `meek'.

You can customize this variable.