Download & Create Disk:

Download latest RetroPie package

Write image to MicroSD (ApplePi-Baker)

Basic Config Setup:

sudo raspi-config

Expand Filesystem
Change User Password
Internationalisation Options
Change Locale es_US.UTF-8
Change Timezone
Change Keyboard Layout
Generic 105-key (Intl) PC
Overclock Pi2
Advanced Options
Memory Split 512

Make sure you have the latest:

sudo rpi-update

sudo reboot

sudo apt-get update && sudo apt-get upgrade -y

sudo apt-get install vim (I’m just used to it and I hate nano)

Setup wireless:
sudo vim /etc/network/interfaces

auto lo
iface lo inet loopback
iface eth0 inet dhcp

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wpa_psk *********

Clean up Boot Process:

sudo vim /boot/config.txt

Uncomment: disable_overscan=1 (This will remove the black borders to boot screen)
disable_splash=1 (Add to the end of file. This will disable the rainbow test pattern at bootup)

sudo vim /boot/cmdline.txt

Remove: console=tty1 (This will not show the linux kernel booting to the main screen)
Add: vt.global_cursor_default=0 (This will disable the blinking cursor at bootup)
Add: logo.nologo (Add to the end. This will remove the Raspberry Pi logos at boot)

Clean up the console:

sudo vim /etc/motd (Remove every line in this file)
touch ~/.hushlogin (This will remove more console prompt nonsense)

Retroarch Settings:

sudo vim /opt/retropie/configs/all/retroarch.cfg

Remove all onscreen display messages (OSD, like controller configurations in yellow text at startup of each game)

# Enable usage of OSD messages.
video_font_enable = false

Setup PS3 DualShock Controller:

The controller will work VIA USA with no configuration needed. If you want to connect VIA Bluetooth you will need to set it up.

sudo ~/RetroPie-Setup/

Reference docs

sudo nano /var/lib/sixad/profiles/default

enable_leds 1
enable_joystick 1
enable_input 0
enable_remote 0
enable_rumble 0
enable_timeout 1
led_n_auto 1
led_n_number 1
led_anim 1
enable_buttons 1
enable_sbuttons 1
enable_axis 1
enable_accel 0
enable_accon 0
enable_speed 0
enable_pos 0
timeout_mins 30

Mega Drive to Genesis:

sudo vim /etc/emulationstation/es_systems.cfg

Change the following:

<fullname>Sega Genesis</fullname