The International Space Station orbits the Earth once every 90 minutes; but don't expect to see it that often! Sometimes it passes overhead in the daytime, when you can't see the station anymore than you can see any bright star. Sometimes the station passes over in the dead of night, when it is cloaked in darkness.
To see the station, we on Earth need to be in darkness, while the station (220 miles above us) catches the light of the Sun. So good viewing times are either around dusk or around dawn.
The station will appear much as any satellite, a bright point of light moving steadily across the sky, visible for up to six minutes.
There are several excellent web sites for ISS passes. Here are three we highly recommend:
This site is one of the most accessible sites for information about the ISS and other satellites. You can select from a wide choice of places on Earth. You can then pick fly-over information for the space station, Mir, or Hubble Space Telescope. You can also get the schedule for Iridium flares, while they still exist!
While the site only lists the next 10 days worth of passes at a time, if you hit 'next' it will give you the next ten days, then the next ten, and so forth.
This site gives you the brightness of the space station for a given pass, where it will appear, reach its greatest elevation, and disappear.
A big bonus of this site: if you click on the date for a given appearance, the site will provide a star map which shows the path of the station.
This site gives information on every pass of the station, even when you cannot see it.
This site depicts the location of the station over the Earth at present.