I\'ll echo what vincenti said.
If you\'re painting an army though and want stuff fast, here\'s what I do for knocking out loads of great table-quality stuff.
-Prime white (do two thin coats of primer. Don\'t try to make it pure white or else it will be too thick, just try to get an even, bright coat)
-Airbrush (or just paint it on thinly) Kommando Khaki or Space Wolves Grey. Choose if you want a warm shade or a cool shade.
-Wash with Gryphonne Sepia or Shadow Grey (GS for the warm white, Shadow Grey for the cool white).
-Mix up a spare pot with 75% White and 25% of your basecoat color. This will be very close to white but not all the way. Built your highlights up to this and stop there. This will allow for some contrast with the final highlight.
-Finally go in with pure white on the very edges.
Something that is really enforced with 2d art is that nothing is ever pure white. Even white will have highlights, so in order to account for that you must slightly darken the rest, otherwise highlights won\'t show up. Don\'t ever use just grey for shading, but introduce warm or cool colors for shadows.