Some specific Instructions:

Contents of /etc/network/interfaces:

auto lo
iface lo inet loopback

allow-hotplug eth0
iface eth0 inet dhcp

allow-hotplug wlan0
iface wlan0 inet manual
    wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
    post-up ifdown eth0
iface default inet dhcp


Contents of /etc/wpa_supplicant/wpa_supplicant.conf:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="YOUR_SSID_HERE"
    psk="YOUR_SECRET_PASSPHRASE_HERE"
    id_str="SOME_DESCRIPTIVE_NAME"
}


Honest.  Those two files, with given contents are what I use on all my pi's.  They boot and immediately connect to my wireless router.  DHCP negotiation provides an address, and my router resolves the hostname to the proper IP address.   Make sure to name each PI appropriately via /etc/hostname.

The weirdness in the 'interfaces' file in the trailing 'iface default...' is needed, otherwise the wireless wpa connection won't come up.

The wpa_supplicant.conf file can have multiple 'network={' entries too, I used to take my pi to work... plug it in and voila, it connected automagically there too, work's configuration was a bit more convoluted though.  Included here as an example, add/replace the following in the wpa_supplicant.conf file:

network={
    ssid="THE_OFFICE"
    scan_ssid=1
    key_mgmt=WPA-EAP
    eap=PEAP
    identity="WORK_USERNAME"
    password="WORK_PASSWORD"
    phase1="peaplabel=0"
    phase2="auth=MSCHAPV2"
    id_str="SOME_DESCRIPTIVE_NAME"
}


Essentially, it scans the wpa_supplicant.conf file and connects to the first network it finds that matches.  Very handy.  It's possible to make it connect to any 'open' network automatically this way too.  Not the smartest thing to do, but do-able.

Prepare SD card for Wifi on Headless Pi
Is it common to include Login / Sign Up actions on an app's splash screen? Or is it more efficient to first have a Splash screen, and then follow with a dedicated Log In / Sign Up page?
