Visio is the most common when one needs to draw a schematic diagram, however, it does not look very good. What software can you recommend to replace visio?
I have taught many systems analysis and design courses as well as other information technology courses, where many diagrams are drawn. So I frequently teach students how to use Visio and other tools. There are many alternatives to Visio. For example, the following are slowly becoming more and more popular (see the links below).