Drink heaps of water, with a bit of lemon in it if it helps. But, yeah, just loads and loads of fluid.
Rest. A lot.
I also swear by dried cranberries, I dunno why, but they can't hurt, right?
Eat loads of vegetables. Fresh ones. Get someone to make you an enormous pot of vegie soup.

They all sound really simple, I know, but it's from a family who does this all the time and never gets sick. Well, we do, but the sickness never takes hold.