Iridium Flares (bright reflections from orbiting communications satellite panels) are a VERY localized event. An observer only a few miles from the location of a Flare that you can see brilliantly, may not see anything at all.
To find when an Iridium Flare (or ISS fly-over) is happening at your location, do this:
1) Get the Latitude and Longitude of the viewing location (your driveway, an outreach event location, etc.) from here: http://www.getlatlon.com/
2) Create a free account at http://Heavens-Above.com.
3) Edit your Heavens-Above profile, and set the Latitude and Longitude of your location.
4) Return to the Heavens-Above home page, and pick which satellite you’d like to see.
5) For a real challenge, try to spot a daytime Iridium flare.
6) Tell me if you saw one!
I also HIGHLY suggest using Stellarium.