1. Avoid close contact.
Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
2. Stay home when you are sick.
If possible, stay home from work, school, and errands when you are sick. This will help prevent spreading your illness to others.
3. Cover your mouth and nose.
Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.
See more here: http://www.cdc.gov/flu/protect/habits.htm