To use Jing you must download and install the free software for your Mac or PC. Once it's installed, launch it and it runs in the background until you need it. You'll know that Jing is ready for you to use because you will notice an orange ball in one of the top corners of your screen. It takes up very little screen real estate and is ready to use whenever you need it. The image below is an example of a screen capture I created with Jing.
You can also use Jing to record a video of your screen. Simply select the area of your screen that you would like to show, click the record button and begin talking. Jing will capture everything you say and do for up to five minutes. A free Jing account allows you to store your videos and screen captures. For $15/year you can upgrade to a "pro" version which will allow you to resize videos and share them directly to YouTube.
Although Jing is good for creating video screencasts, I actually prefer ScreenToaster for making video screencasts. ScreenToaster is a free, web-based, service for recording your voice and the actions on your screen. Just as with Jing, you can specify how much your screen you want to capture. I prefer ScreenToaster for making video screencasts because I can instantly upload to YouTube as well as have immediate access to the embed code for my videos which I then place in my blog.
Applications for Education
Jing, ScreenToaster, and products like them are very useful for enhancing written instructions that may have to give to students to show them how to do something like comment on your blog. Words work well for giving directions, but just as in any how-to manual, images can make all of the difference between confusion and clarity. This is particularly true if you have some struggling readers who might otherwise be confused by trying to follow written directions.
I've found Jing to be very useful when I'm giving directions in a professional development workshop. Posting annotated screenshots to a wiki gives every participant a reference for later use. I've especially found this to be true when teaching about Google Earth because there are some many things for first time users to explore that they sometimes get confused and need a reference of the basics. That is why I used Jing to create all of screen images found in Google Earth Across the Curriculum.