It is important that students make charts and diagrams themselves, and use their own creations as tools for doing more abstract calculations. The temptation is to simply hand out copies, but, in this case also, making their own visuals slows down the pace of presenting the concepts, puts the student in control of the pace, and builds associations in the student’s mind as the visual is being made.
Even something as simple as a times table chart will have more meaning if students make their own, rather than you handing it to them.
The best way for students to learn to read graphs and pie charts is to make many of them. Learning to make charts or bar graphs or line graphs can be taught in math class, but they can be assigned in other classes as well. You may have software available that students can use, or go to this web site that allows students to make all sorts of graphs and charts: http://nces.ed.gov/nceskids/createagraph/
I like to assign a graph or chart every day for a month or longer, starting with bar graphs to compare two (or more) things, then a line graph to show how something has changed over time, and then a circle graph to show how a whole thing is broken into parts. I provide some data, ask for the essentials (below) and students decide on what labels to use, what colours, what type of chart. I ask them to post their finished charts, and we take a look at what makes a chart readable. I don’t point out any errors, or make any critical comments. I comment on what makes various charts great. For example, I might note that the bold colours on Mary’s chart make it easy to see the difference between the columns, or that the clear title on Pete’s makes it easy to understand what the graph is showing, or that the large scale of Mustafa’s makes it easy to take everything in.