Icomplete global minor mode provides a convenient way to quickly select an element among the possible completions in a minibuffer. When enabled, typing in the minibuffer continuously displays a list of possible completions that match the string you have typed.
At any time, you can type C-j to select the first completion in the list. So the way to select a particular completion is to make it the first in the list. There are two ways to do this. You can type more of the completion name and thus narrow down the list, excluding unwanted completions above the desired one. Alternatively, you can use C-. and C-, to rotate the list until the desired buffer is first.
M-<TAB> will select the first completion in the list, like C-j but without exiting the minibuffer, so you can edit it further. This is typically used when entering a file name, where M-<TAB> can be used a few times to descend in the hierarchy of directories.
To enable Icomplete mode, type M-x icomplete-mode, or customize
t (see Easy Customization).