The first thing you need to know is the entire festival is EXTREMELY graphic. The half-ton bulls goring whoever they can. The bullfights. The excessive drinking. The protests. If you've got a good head on your shoulders, you'll be just fine.

PLANNING
To coincide with my 30th birthday, we decided to attend the 2009 Running of the Bulls in Pamplona, Spain. Two years prior we started planning where we were going and how to get there. Once we booked our hotel, we then booked flights. (The Festival was July of 2009. We booked hotel and flights in November of 2008.)
GETTING TO PAMPLONA
Our airfare would have been over $1,000 per person (Chicago to Switzerland to Madrid), but we used frequent flier miles to save the cost. As mentioned earlier, we booked our flights in November and had no issues with using airline miles. One of the other guys meeting up for the festival decided last-minute to join up and his flight was $800 (Chicago to Dublin to Barcelona).
In Europe, you can mostly show up at a train station and purchase tickets in the hour or so before your travel. This is not the case with getting to Pamplona for the festival. Make sure you get your train tickets in advance. (We bought

LODGING
We stayed at the Gran Hotel la Perla, which one side faces the Plaza del Castillo, the other side is on Calle Estafeta, which is were the bulls run. The hotel wanted their money -- paid in full -- at the time of booking, through a wire transfer to their bank. The cost of a room with a balcony on the route was six times what the "off-season" price was. The six of us fit snugly onto our balcony. (The four others split two rooms at a hostel for 200 euros per night, with a shared bathroom.) http://www.granhotellaperla.com
THE FESTIVAL
One account I read about the Festival of San Fermin was how many days to stay for the Running of the Bulls? The suggestion was four days/three nights. I think it was the perfect amount of time. We arrived in Pamplona the night before the opening ceremony (trying to make it for the Running of the Nudes), then left after the second bull run.
PETA leads a protest "Running of the Nudes" through the bullrun route on noon on July 5th. It's their way of drawing attention to the cruelty the animals face. (It seems to be a hybrid idea between protesting and the old saying "If you can't beat 'em, join 'em.") We did not make it to Pamplona in time to see the nearly-naked folks run down the street, but everything I've read says its not a violent or angry thing by any means, its sort of the "Opening Act" to the party. http://www.runningofthenudes.com/
The festival begins on July 6th at noon in the main plaza of town, Plaza Ayuntamiento. If you want to be in the plaza for the celebration, arrive no later then 10:00 AM. Do not wear jewelry (this includes earrings, necklaces, bracelets, etc.), nor should you bring along your purse or a backpack. Close-toed shoes are a must with all of the broken glass. Anyone claustrophobic should rethink about going to watch opening ceremonies from the plaza. Whatever you wear will get soiled with a variety of things. At 12:00 a rocket is fired into the air and everyone holds up their red bandanas to salute San Fermn. At this moment, the crowd starts to dispel and now it is acceptable to wear your bandana around your neck (its normally worn around the wrist until the festival begins).

RUNNING OF THE BULLS
The bullrun occurs every morning at 08:00 AM from July 7th through 14th. The bulls start near the church on Cuesta de Santo Domingo, turn left on Mercedes (in front of the town hall), turn right onto Estafeta, left on Telefonos and into the bullring they go. There are six bulls are four hefers. If you're not going to run with the bulls, be in position to watch along the route by 06:00AM at the latest. Bring a sweatshirt you don't mind losing, perhaps a deck of cards to pass some time, and maybe something to read. The church on Cuesta de Santo Domingo is one of the best free places to watch from. If you'd like to watch from the bullring, there are monitors set up to watch the bullrun (televised nationally every day) before they get to the bullrun.
If you are planning on running, please be smart about it. There are websites out there which have pretty good information on the safest parts of the route to run, and what to expect. Time-wise, I never really saw a time-table of what to expect for the Running of the Bulls. Here's what I saw while attending:
07:30AM the streets are cleared of the drunk people milling about. (I felt sorry for the people who were there ready to run, only to be cleared away by the police.) After the streets are cleared of people, debris and trash is cleaned up by the street sweepers.
07:50AM those willing (and sober enough) to run are allowed to take their positions on the route.

If you're going to run, wear good running shoes and enter the route in the designated entry areas. Know that people are aggressive as they run; every "bull versus man" incident we saw was a result of a runner tripping over another runner and wiping out in front of a bull. (This is one of the reasons why I didn't run. I knew I could out-run a bull, but the guy I saw shoving other runners out of his way was a concern to me.)
BULLFIGHTS
We paid fifty euros to a scalper to sit five rows from the back on the shady side of the bullring. The sunny side was chaos and awesome to watch from our vantage point. The bull fight was not-so-awesome to watch, as anyone can win when its eight versus one.
Overall, the Running of the Bulls was an awesome experience. At the bullfight, we sat next to an old Spaniard who filled us in on the goings-on for the festival. He ran with the bulls that morning and the previous twenty-two years as well. He said Pamplona was his number three party on the list, after Carnival in Brazil and Oktoberfest in Germany. As for our party, it was an awesome experience. I don't need to do it again, but I'm so glad to have been a part of it. We didn't run, but didn't need to with a spectacular balcony overlooking the longest stretch of the route.

That's our trip in a nut-shell; some pictures are online in the photography section. Make your trip your own adventure and take a lot of pictures along the way.
And send home postcards. Everyone loves postcards.