I was doing a little reading about the flu in 1919. I found a nice article from the New York Times describing how doctors at the time were predicting an outbreak based on last years (1918) outbreak. 
There are two pieces of advice given in this article that can apply to us 90 years later:
1. “those who are weak are advised to build up their strength”
2. As a preventative …exercise, good food and vigilance”
That is solid advice. Today doctors focus on a vaccine that may not even work. Last year doctors “still recommend getting the flu shot even if it doesn't prevent you from getting sick.” There must be a reason most doctors don't get the flu shot themselves?  Maybe it’s because the flu shot does not protect kids . It’s also not so effective in the elderly.
So what do you do? Listen to the doctors from 1919. Since it’s well known that moderate exercise will always boost your immune system? I would start there.
If your doctor has been in practice since 1919 you may get some good advice about prevention of the flu. Otherwise do your homework. Get proactive in your health with exercise, good food and vigilance.
-  http://query.nytimes.com/mem/archive-free/pdf?res=9D05E5D81338EE32A25756C1A96E9C946896D6CF
-  http://abcnews.go.com/GMA/ColdFlu/story?id=4334018&page=1
-  http://www.nytimes.com/2008/09/02/health/02flu.html
-  http://www.associatedcontent.com/article/1285437/many_doctors_push_flu_vaccine_dont.html