These notes are for use when it is required that a device automatically starts, runs an x-session and then runs a particular task.
For example an information display. In those situations it may also be required that the screen does not blank.
Auto Login

Notes from http://elinux.org/RPi_Debian_Auto_Login

sudo nano /etc/rc.local

su whateverusername -c startx

Stop the screen saver

Notes from http://raspberrypi.stackexchange.com/questions/752/how-do-i-prevent-the-screen-from-going-blank

install xset apt-get install x11-xserver-utils

open or create ~/.xinitrc

xset s off # don't activate screensaver
xset -dpms # disable DPMS (Energy Star) features.
xset s noblank # don't blank the video device

exec /etc/alternatives/x-session-manager # start lxde

Auto run

Notes from http://blog.flowbuzz.com/2012/07/raspberry-pi-and-autostart.html

cd ~/.config

mkdir autostart

then creat file called .desktop

format of contents is

[Desktop Entry]
Type=Application
Exec=/filetorun