I do it Didger's way, but with lens hoods as well. Even if you use a hood, it's important to make sure no direct sun is getting by it and hitting the glass. In other words, don't assume everything will be fine because you are using a hood.
Lens hoods for zooms are especially marginal, because they have to be designed for the wide-angle end of the zoom range, and thus provide much less protection than you could safely use at the other end.
I think Lisa is right, too: If your camera is in the open on alightly overcast day (no direct sun), a good lens hood (or Didger's hat, or both) can make a big difference in the amount of flare.