The International Space Station is always circling the Earth but isn't always exactly visible to us. In the daytime the Sun drowns it out, at night the Earth shadow usually covers it. This week though, you'll be able to see the ISS streaking across the evening sky.
How do you tell? Well, it's going to be the brightest object up there other than the Moon (and maybe UFOs).
Plug in your location here to find out when it crosses your way and be sure you look up when NASA tells you to because it'll only be going around for minutes at a time (it moves fast, that space station). [NASA via Wired]