Make sure the typing function is easy to use. So many of the less-expensive models skimp on the keyboard. We know one media specialist who was very disappointed when her mail-order character generator arrived. The keyboard was so small that she had to type using the enclosed metal toothpick. Look for smooth movement and adjustable speed.
Some models allow more sophisticated text movement.
Check this feature on your prospective purchase. If you're creating a school news show, look for the separate preview channel. Find the video output of your character generator. The VCR may even be connected to your school's closed-circuit distribution system. In fact, many schools use a character generator to display a scrolling announcement message throughout the day.