If i ever feel like i am about to get a cold, i take 1500mg for vitamin C; when I wake up and when i am about to sleep. I also drink some herbal tea, and eat a lot of healthy meals. Also don’t do anything stupid like go skiing while you’re sick, it might be worth it for that day, but 2-3 days later you will be regretting it when u feel like shit. Also drink alot of OJ and water throughtout the day, and most importantly a good night sleep.