Beginner trying to make 12 volt water pump work

Hi im a beginner with Arduino and need a SIMPLE diagram of how to set this up please for an art project for someone.

I have an Arduino Duemilanove and a 12 volt car screen washer water pump.
The idea is to fill up a tray with water then the pump switches off to let the water drain away and then to switch on again etc.
I need to pump water from the reservoir for say 5 seconds then stop for say 10 seconds but this would have to be changeable to suit the flow pressure.
I have the basic blinking led light and thought it would be easy to do using those parameters that control the led speed. But not so as I realise now.
Can anyone tell me a simple way to do this with pictures please lol.
Many thanks
Andye

Search the board for "MOSFET".

Or search for "Water Pump", also in the last week.

You probably only need to switch the pump on and off.