If you are seeking to keep a ZeroInbox with a little more ease, I have tested a tool which can be a bit more helpful in the followup process.
The tool is FollowUp.cc which has a simple function. It puts your emails into a queue that comes back to you at a specified time.
For example, if you send someone an email requesting action, you can BCC email@example.com to receive a reminder back in your inbox in a day.
This keeps you from having to remember to check back and you are using your inbox to create action for yourself.
For those using Google Apps, this allows your Gmail inbox to become a tickler file for followup and further enables you to use your Google Apps Mail as a CRM for sales.
There’s a whole selection of logic for timeframes to receive a reminder with a simple email copy. There is a menu selection to further delay the followup reminders as well.
I liked the ease of use and how frictionless the experience was. I could simply defer items that I was not ready to deal with at the moment and focus on what the day presented knowing that a later time when I was ready to act would prompt a reminder.
You can try it out and see how it works within your world to increase productivity. In a sense, it is an automated secretary and can greatly help a sales process which requires the right touch points at the right time.