Some write it down manually in a logbook. Others prepare a spreadsheet. But let me tell you of a better and more convenient way.
Many time tracking tools are available if you search for it. But what I recommend is a great program like Easy Time Tracking.
How good is Easy Time Tracking?
Well like most time logging apps, Easy Time Tracking does what most can do and even more!
You can organize your tasks, keep up the schedule and check how much time to carry out a given task, create reports, and lastly, a great addition– it helps you create a fast, presentable and easy to do invoice ready to be sent to your Client.
Learn how to do it with this tutorial: