Kudos for mentioning the Hemingway app, I desperately needed something like this. I tend to write longer sentences, which is perfectly normal in my native language, but they often sound a bit off in English. This app should definitely come in handy when editing stuff! 

To touch upon the topic itself, I don't really use any specific tools for writing. I write all my stuff in Word, mainly due to its autosave feature, and use PiratePad for collaborating. I used to keep physical notes as well, but my handwriting is so horrible that I can't read half the shit I've written down.