Minibuffer
C-x ^ make it taller in the normal fashion
completion commands in minibuffer TAB/SPC/RET/?
? (minibuffer-list-completions)
TAB (minibuffer-complete).
SPC (minibuffer-complete-word)
RET (minibuffer-complete-and-exit)
Minibuffer History
up (previous-history-element)
down (next-history-element)
M-r regexp RET (previous-matching-history-element)
M-s regexp RET (next-matching-history-element)
Repeating Minibuffer Commands
C-x ESC ESC (repeat-complex-command)
M-x list-command-history Display the entire command history
http://snebulos.mit.edu/htdocs/emacs.html
http://www.gnu.org/software/emacs/manual/html_node/emacs/index.html#Top