Checkdoc, Package Developing, and Cakes28 Jun 2014, by Artur Malabarba.
You're not a true Emacs package developer until you run
checkdoc through your packages. You'll be amazed at the
number of style errors it finds. Unfortunately, not enough
adepts are aware of this tool, perhaps because it's more of
an icing spatula than a carving knife.
Just visit your package file and run M-x
It runs through the buffer and pinpoints style and spelling errors in your docstrings and comments. It won't change the taste of your chocolate cake, but it will give the icing that lovely silky smoothness.
As Grant Retke and lunaryorn were kind to point out in the comments, Flycheck does checkdoc for you.