Top things to PREVENT the Flu or spread of the flu.
(1) Get the Flu shot! I Was never big on them but I got the flu for the 1st time and WOW! yeah, I'll be getting those from now on. It takes upwards of 2 weeks to work so get it as soon as ya can! It doesn't mean you wont get the flu, but if you do, it'll be way less of a horrible thing.
(2) Tamiflu! If someone in your house gets the flu and you haven't had the shot, take Tamiflu ASAP! It's prescription but it'll help prevent and lessen the effects of the flu.
(3) Take those vitamins! Keep your immune system happy and healthy. A simple multi-vitamin everyday. Drink good juice (like fresh OJ). Have your days' food be all balanced. I really think this is what kept Hunter from being the only kid who didnt get sick (even with a cold).
(4) Sanitize! After the bathroom, after touching someone germy, after touching a tissue... I'd go as far as using sanitizer, letting it dry, then washing my hands in hot water with soap before touching food a well kid was going to eat.
(5) SPACE! Make sure you're not crammed into people and there is good ventilation. Keeping the temp on the cooler side will help hinder the growth and spread.