bookmark-save-flag is a variable defined in `bookmark.el'.
Its value is

Controls when Emacs saves bookmarks to a file.
--> nil means never save bookmarks, except when `bookmark-save' is
explicitly called (M-x bookmark-save).
--> t means save bookmarks when Emacs is killed.
--> Otherwise, it should be a number that is the frequency with which
the bookmark list is saved (i.e.: the number of times which
Emacs's bookmark list may be modified before it is automatically
saved.). If it is a number, Emacs will also automatically save
bookmarks when it is killed.

Therefore, the way to get it to save every time you make or delete a
bookmark is to set this variable to 1 (or 0, which produces the same

To specify the file in which to save them, modify the variable
`bookmark-default-file', which is `~/.emacs.bmk' by default.

You can customize this variable.