The "hello world" of the GPIO project is wiring three LEDs, three 560ohm resistors to three GPIO pins and GND. Then writing a python program using RPi.GPIO to run the LEDs as a traffic light sequence.
Stage two is reading the status of a switch and lighting or extinguishing an LED.
http://raspi.tv/2013/rpi-gpio-basics-7- ... -tutorials
has some details (and links to six earlier tutorials by Alex). Those will teach you the basics of wiring and programming.