Wash hands after handling each horse.
Use boot washes to scrub manure from shoes prior to entering each stall (walk-thru foot baths are not effective).
Sharing equipment (e.g., buckets, tack. brushes and stall cleaning equipment) among horses should be avoided (shared equipment must be cleaned, sanitized and drained between each use). Ideally, each horse should have its own equipment that is not shared.
Avoid nose-to-nose contact between horses.
Wheel barrows should be used for either food or waste, never both.
Limit people entering the barn to only those who are necessary.
Clean and disinfect stalls between each occupant.
Vaccination should be part of an ongoing preventative program but is not advised for horses that have been exposed to or are incubating the disease.
Keep hose nozzles out of the water buckets and troughs. The practice of submersing the hose nozzle has been identified as a major factor in outbreaks in large stables.
Control flies and other pests that can carry contaminants from horse to horse.

Additional Resources:

General Biosecurity