The International Space Station is, after the sun and the moon, the third brightest object in the sky. If you know where to look for it, you can easily see it -- no telescope required. But: if you know where to look for it. Since the Earth spins as the ISS orbits it, the station's position in the sky at any given moment -- relative to a position on land -- is hard to know for sure.
You know who always knows where the ISS is, though? NASA. Several times a week, Mission Control at the Johnson Space Center in Houston determines sighting opportunities for 4,600 terrestrial locations worldwide -- places from which the space station is visible for a long distance. Now, NASA is publicizing that list ... and sending it, in fact, directly to you. Spot the Station lets you sign up for email or text-message alerts that will let you know, a few hours beforehand, when the ISS will be passing over your area.
"This service will only notify you of 'good' sighting opportunities, NASA says -- "sightings that are high enough in the sky (40 degrees or more) and last long enough to give you the best view of the orbiting laboratory." That viewing opportunity could come as often as once or twice a week or as rarely as once or twice a month, depending on the Earth's rotation and on sky clarity. (So "don't worry," NASA says, "if there are big gaps in between sightings!")