I always refer to my tasks lists for action reminder information; and I keep any related action support information in my email folders (@Action Support, @Waiting For, etc.)... (I'll always make a note in the task itself if there is information associated with the action, and where it can be found (both digital and paper-based).
For example, for waiting fors I always copy myself on emails, and then create a task as the Waiting For reminder. I don't just dump it into a Waiting For folder. The key is to make sure there aren't action reminders buried elsewhere, and that they're all captured in your lists somehow.