Generally, I'd say: keep it short and digestible. Also watch out for extra noise on the screen, otherwise it'll distract the viewer. And having an ending transition can be useful for understanding when the gif is done, since their looping nature can make this aspect confusing.

Software: Typically Screenflow. It has a built in Gif preset which I'll sometimes use, or if better compression is needed: https://gist.github.com/dergachev/4627207