“If you do fall to the ground, lie still, and cover your head with your hands until the danger has passed.”
Visit Your Guide to San Fermin for other helpful tips. The section on Food, Drink and Sleeping is pretty comprehensive, though you might want to check out the section titled “Watch Out!” Maybe. Of course, perhaps you’d rather not know about the danger of a nighttime stroll along the city walls (you might fall off, the guide warns, particularly if you’ve “had a drink too many”).
Also check out more handy info on the running of the bulls, including daily photos, injury reports, statistics on past runnings, etc.