Go here for simple switch diagrams...
http://en.wikipedia.org/wiki/Switch
Most Switches are SPDT (Singe Pole Double Throw) meaning that one wire (Single Pole) may be routed to either of two outlets (Double Throw). Switches like this are often marked with Com, L1 & L2. The Com terminal may be connected either to L1 or L2 depending on the position of the switch toggle.
To achieve what you want to do, your best approach is to fit a simple in-line switch like this one...
http://www.mr-resistor.co.uk/admin/uploads/297/2792_switch101white1_297.jpg
Please remember Lord Finchley.
Lord Finchley tried to mend the Electric Light
Himself. It struch him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisian.
Peccavi
February 2009