I start with Google Keep on my phone. With the on-screen widget, this app is the fastest thing for jotting down a note. It seamlessly syncs to a cloud backend without having to press save or send. Writing a note down as quickly and easily as possible is probably the most important thing for me. If it's too hard or slow to jot down a note, I will inevitably: 1) forget what I wanted to note, 2) forget what I was doing before I was writing the note, or 3) give up on writing down notes.
With that said, another "killer" feature of Google Keep is the ability to set reminders. This feature transforms Google Keep into a light-weight appointment calendar. Another nice feature is the ability to archive notes. This helps me keep the most important notes in the foreground, while letting old notes fade into the background. I often combine these two features to push a thought into the background (archive a note), but knowing that I will revisit the subject later (by setting a reminder).
At the end of every day, I transition my notes in Google Keep to files in my Dropbox folder. I do this by opening the web version of Google Keep and using the terminal to view my local Dropbox folder. I review notes in Google Keep and update corresponding files in Dropbox. Where Google Keep is used for the more recent things that were on my mind, I use the files in Dropbox for more long term notes. Of course, the nice thing with Dropbox is that I edit local files that I know are being backed up in the cloud (all auto-magically).
The last thing that I haven't found a good solution for is an app for sharing notes. Trello seems like the leading candidate, but I haven't used it enough, with others, to be sure.
