When it comes to the practical act of writing, use whatever works for you. As long as you're doing the writing, you're a writer. Whether that means using pen and paper, dictation into a microphone, Microsoft Word or Google Docs is up to you.
The key is to find a process which gets out of the way. I can't write by hand simply due to my appalling handwriting, while I've always found Word to be inefficient for long form projects.
Therefore there's one app I would urge everyone to at least try: