My $0.02 on staying away from illness....
-Take vitamins and/or supplements. Personally I only take natural vitamins versus lab created shit. My vitamins are produced by Standard Process:
http://www.standardprocess.com/index.asp
-Drink lots of OJ
-A cup of coffee won't hurt ya because of the anti-oxidants it contains.
-If you have a sore throat, chest cold, etc, forgot about throat drops and all that fun stuff. I try my best to only use Sasco Aloe-Lyptus creme as it does wonders the above and colds in general.
-Avoid processed foods and fast food (preservatives in general if possible).
-Eat lots of fruit, especially apples.
-Drink lots of water. I have started carrying a water bottle with me throughout the day and I'd venture to guess that I'm drinking at least 1 gallon of water each day now.
-Quit smoking