While you are out there looking for ISS, you might as well look for other exciting sights in the night sky!
On a clear, moonless night, well away from city lights, you can see about 4,000 stars. Remember that every star is in fact a sun, comparable to our own sun, although many stars in the night sky are actually more luminous than the sun.
The Milky Way
The Milky Way is a broad, hazy band of light stretching across the sky. It can only be seen on dark, moonless nights. What you see is the combined light of myriads of distant stars. In fact, the Milky Way is the inside view of the Milky Way galaxy in which our sun (and all other stars in the night sky) reside.
The Magellanic Clouds
If you live in the Tropics or in the southern hemisphere, you will sometimes notice two small, diffuse clouds of light, not too far from the Milky Way. These are small companion galaxies of our own Milky Way galaxy, first described by Magellan.
Officially known as meteors, 'shooting stars' have nothing to do with real stars. The brief streak of light that you see is the result of a tiny grain or pebble from interplanetary space that enters the Earth's atmosphere with high velocity.
Depending on its orbital position with respect to the sun, the moon is visible for a smaller or larger part of the night. At an average distance of 384,400 kilometers, the moon is actually Earth's nearest neighbor.
While stars are in fact distant suns, planets are smaller and cooler bodies that orbit our own sun. They shine by reflected sunlight. The planets Mercury, Venus, Mars, Jupiter and Saturn are usually brighter than the brightest stars in the sky. Because of their orbital motion, they slowly move with respect to the 'fixed' stars.
As a result of Earth's rotation (one revolution per day), the night sky appears to slowly rotate. This can easily be seen in five or ten minutes time. For observers on the northern hemisphere, the apparent hub of the celestial sphere is very close to the Pole Star, which is always due north.
The International Space Station is not the only Earth-orbiting satellite that can be seen with the naked eye. On average, you will be able to see another satellite every five to ten minutes or so. However, most of them are much fainter than ISS.