I found the answer at "Do It Yourself.com/How to Install a light switch"
http://www.doityourself.com/stry/h2installswitch
INSTALLING THE SINGLE-POLE TOGGLE SWITCH
The simplest switch system – the single-pole toggle switch The ordinary single-pole toggle switch provides a means for breaking or feeding electrical current to a light, appliance, etc.
The single-pole toggle switch has two brass terminal screws. One wire (usually the black) is cut, then is connected to the two brass terminals. The other wire (white) is uninterrupted from the power source to the light or fixture.
When connecting a wire to the terminal screw of a switch, always turn the loop on the end of the wire in the same direction as the screw threads, as shown in illustration (A). If the loop is turned in the opposite direction (B), tightening the screw will loosen the loop.
If the wire connects to the terminal screw and then runs on, cut and strip the wire on both sides of the cut. Using a 6" piece of wire with both ends stripped (sometimes called a pigtail) and a wire-nut, fasten the three wires together. Connect the pigtail to the terminal, as in the figure.
Use wire-nuts or screw-on connectors to save time and effort when you must make a splice in any electrical wire. Always cover any soldered connection with insulating tape. If soldered sections are rough, apply an extra layer of tape. Insulate the wire an additional inch or two beyond the soldered connection in each direction.
White wires should generally be attached to light colored terminal screws such as silver. Black wires should generally be attached to dark colored screws such as brass colored. If the terminal screws are the same color, either wire can generally be attached to either terminal. Green terminal screws are for grounding wires.
