This came through one of my lists: "Feel flu symptoms coming on? This can help: Take high-dose vitamin C (4,000 mg), zinc, vitamin D and a healthy serving of medicinal herbal tinctures such as black elderberry or astragalus. Go right to bed and allow yourself as much sleep as you need (even 10 - 12 hours). This can often stop the flu right in its tracks."
Personally, I take 5000 mg of C appx once an hour (whenever I think of it) for cold/flu/sore throat. C is one of the vitamins where any excess just comes right back out, you can't overdose, and some doctors administer as much as 50-100,000 mg per day for critical cases. Lots of tea (or hot lemonade) with honey, alternating with chicken soup.
And of course, as much sleep (or at least rest) as you can manage.