It was particularly impressive once when we caught the shuttle tracking behind it after it had finished a mission and parted for home.
Anyone wanting to know how and when to track it in your area can go here for the schedule:
http://www.heavens-above.com/Click on "from database" under Configuration, and click on your country, then select your precise location by entering it into the search string box. Even our little bitty town that's not much of a town is in the data base. Then when you are done, it will return you to the home page and click ISS under Satellites.
How to read the chart:
Date is, of course, self explanatory.
Mag. means magnitude. Anything expressed in a negative figure is going to be brighter. For example, a -3.0 is going to be brighter than -0.3
Start is the time it should begin to be visible to you.
I'm not too sure how the Altitude figure is interpreted exactly. Az. is for Azimuth and refers, I believe, to the curve of the trajectory, if I'm not mistaken, and tells you which direction in the sky to look for it in it's arc, beginning to end.
It's easy to discern as it tracks very smoothly and really high, higher that air traffic and there are no blinking lights. Just the sun shining off of the reflective materials of its construction.
It's lots of fun to run outside to see how accurate this all is and watch it track across the sky until it disappears behind the earth's shadow on the downside of it's arc.