Most efficient way to graph quadrics is to use "ImplicitPlot3D" package. 
It is not included in "Mathematica", we need to open "Mathematica 5.2" folder, find "Addons" and 
copy "ImplicitPlot3D" package into "Autoload" directory. 
Any script using ImplicitPlot3D must load the package first: << ImplicitPlot3D`; << Utilities`FilterOptions`;
Also, see "ImplicitPlot3D Notes".