In this Instructable I will show you how to get a very basic GPIO system working with your Raspberry Pi.
For this I will focus on simply controlling an LED.
NOTE: For controlling GPIO via a web browser, click here.
Step 1: GPIO Pinouts
Please note that the DNC connections are actually connected on the board - so don't put voltage on them :D
To turn pin 7 of the header connector on, you set GPIO 4 high.
Note: You can find another pinout image, here.
Step 2: Root account
Firstly you must login to your Raspberry Pi as root. This step will cover how to enable the root account, skip to the next step if you can already do this.
To enable the root account, login to your raspberry pi, then type "sudo -i" and hit Return / Enter. (you'll need to type your password in).
Then type "passwd root" and hit Return / Enter.
You will be asked to type a password, then confirm it.
It will say that the password was successfully changed.
Now you need to completely log out of your Raspberry Pi (Restarting it works as well :D), then login with:
Password: Whatever you just set