Tips and Requirements

Most Important: You must have at least 8GB of hard drive space to play Halo 4 multiplayer.  The second disc in your package contains all the content for War Games and Spartan Ops, and must be installed to the hard drive.  You will not be able to play clan night tonight until you install disc 2.  Disc 1, as far as I can tell, is optional.  Insert disc 2 and choose the option to Play Halo 4.  When it launches, it will give you the option to install.

Very Important: Make sure you get into the Xbox Live Chat party, so that we can talk you through any connectivity problems you may have, independent of the game chat.

[11/7/12 Update]: Disc 2 apparently only requires 4 GB of space to install, can go on your hard drive or a compatible flash drive.