How do I reate a x-y rectangular coordinate graph in Excel

I want to create a line graph/chart in Excel using the rectangular coordinate system. The x-axis is from -12 to +12 with 0 in the center of the graph. The y-axis is from -12 to +12 with 0 in the center also. I want to show the horizontal and vertical gridlines. Then I would like to plot ordered pairs (x,y) for different points on the graph. For example, for a straight lline through the origin, 0, would be: (0,0); (1,1);(2,2);(3,3);(4,4) etc., connecting the points with a straight line. I would like to use this type of graph to represent one or two different lines on the same graph. In this way, I can illustrate to my students different equations of a line in the form of y= mx+b. I am using Office 2007 in Windows Vista. I would appreciate any help with an example.

Wallace