How to undo the most recent commits in Git?

You accidentally committed wrong files to Git, but haven’t pushed the commit to the server yet. How can you undo those commits from the local repository?

$ git commit -m "Something terribly misguided"      
$ git reset HEAD~                                   # copied the old head to .git/ORIG_HEAD
<< edit files as necessary >>                       
$ git add ...                                       
$ git commit -c ORIG_HEAD                           # will open an editor, which initially contains the