There's really nothing you CAN do once you're sick except take some time off and try not to exert yourself. Drink plenty of fluids so you don't dehydrate and eat if you can. Fruit and veggies that are easy on the stomach, and anything with fiber is good. Oatmeal if you can; Metamucil, benefiber or other fiber supplements if you can't - basically, just to make sure you're not squirting out both ends so to speak. Also, fiber is a good thing to eat plenty of anyway.
Do not overload on vitamin C (or any other vitamin) since there's an upper limit your body can handle safely and exceeding your daily recommended dose has shown no positive effect at all despite what quacks would like you to believe. In fact, overloading vitamin C has been shown to cause kidney stones (trust me, these hurt and can cause serious long-lasting damage) and diarrhea. Over-the-counter remedies (like that conjob Airborne) have no affect at all that will help you, so save your money. Anything advertised as 'strengthening your immune system' won't do such a thing, and that's good. If it really could do that, it would be by prescription only since your immune system being too strong is what causes autoimmune disorders like lupus. Antibiotics don't work since the flu and colds are caused by viruses, so don't bother.
Basically, just stay at home, take some soothing hot showers, keep your feet up and try to keep yourself fed and hydrated. Let your own immune system fight the virus and try to enjoy a couple days off, as hard as that might be. Oh, and watch the fever - if you hit the 108 mark (that's 42 for us Canucks) you will get brain damage. If you go above 107/41.6, cool yourself off with a cold shower. If that doesn't work, call a doctor. You should also call a doctor if you find yourself coughing a lot and unable to catch your breath. It's probably not serious (statistically, the ones at risk are children and seniors), but you can get a fluid buildup in your lungs that basically suffocates you. So if you feel like you're suffocating, it's time to seek medical attention. Risks of both fever and fluid buildup are rare in adults, so don't worry about it.
