The mark

[David Vinayak Wallace <GUMBY@MC.LCS.MIT.EDU>]

    Date: Wed, 12 Feb 86 00:57:34 EST
    From: Keith F. Lynch <KFL at MC.LCS.MIT.EDU>

    When I do an incremental search, the mark is set at the beginning
    of the search.  Is there some way to get it to stay where I last
    set the mark with ^@ ?

This only happens if you move a long way.  You can set the threshold
EMACS uses to decide whether to set it by setting the variable auto
push point variable.  c-U c-Space might also be what you want.

All this is available via self-documentation.