Keeping up with multiple freelance clients can be difficult, to say the least, but not having a workable system is a disaster waiting to happen. Sending the wrong assignments to the wrong clients, poor prioritization, and missed deadlines are sure to ensue. This is a system that has worked for me, and maybe it can inspire you to create a system to fit your own needs.
I communicate with clients almost solely by email or Facebook messenger. Occasionally phones calls happen, but they are few and far between. Skype is another popular form of communication, and I have had clients that prefer it. My advice is to set up a separate email address for work, and encourage clients to contact you at that address.
For all other communication, set up a file and save screen shots of messages and Facebook or Skype chats. If you have a phone call, make notes on the call and save those in the file as well.
Create a separate email folder for each client and save all email communication for said client in its own folder. Even when the project is finished, save it. You are covering yourself here, and all emails are more easily accessible for referring back to if needed.
Electronic Files for Each Client
Each client should have its own folder on your desktop. Each project you complete, whether and article, blog post, graphic design, or whatever your finished project may be, should be saved in the appropriate client folder.
Bring it all together with an assignment spreadsheet. It can be as simple or as complicated as you want or need. You can have multiple worksheets or only one. Play with rows, columns, and data to determine what best fits your needs. At a minimum each open project should be listed with the deadline, in order of priority.
Paper Planner, Apps, and More
I have a paper planner, and I find it helpful to write down which projects I am working on for that day as a part of my to-do list. There are also plenty of fancy apps that can be very helpful, but the one I find most helpful it the reminder app that came with my iPhone. I simply set reminders the day before a deadline, and if it is a project that will take more time, I may set one a week out or a couple of days out as well. I do not utilize Google calendar to the full extent, but if you do, something similar can be done with it.
The main thing to remember is, for the most part, do not delete anything. At least be very selective with what you do decide to delete. Have a system for keeping clients and their projects separated, and have a way to see at a glance what you have open and when each open project is due. These simple steps can save you a lot of heartache in the freelance world.