Someone posted a link to the format announcement. Thanks!
The qualifying series will begin with a preliminary round involving the bottom 24-bottom FIFA ranked teams according to the latest edition of FIFA ranking.
The 12 teams to qualifiy from the preliminary round will join the 28 teams, on a bye for the next phase.
The top team from each of the 10 groups will qualify for the final play-off, and will play on home and away basis to determine the five slots.
In all, 154 matches will played between November 2011 and November 2013.
PDF file detailing the qualifying format.
Mauritania are the one team not participating and we'll see Sao Tome e Principe return to competitions after 8 years.
This changes the seeding quite a bit. It also depends on what "latest edition" of the FIFA rankings means. April (since the announcement was made on May 16, before the May ranking was published) or July (the latest edition at the time of the draw)?