1) CDC recommends a yearly flu vaccine as the first and most important step in protecting against flu viruses.
2) Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
3) Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
4) Avoid touching your eyes, nose, and mouth. Germs spread this way.
5) Try to avoid close contact with sick people.
6) If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.)
And finally, never share toothbrushes with another person, and do not store your toothbrush where it can touch another person's toothbrush. This can lead to cross-contamination and the spreading of illness.