Brightest star of the night sky
The best way to find a particular star/planet/etc. is almost certainly to use a star map of some sort.

For example, doing a Google Image search for "star map sirius" would get you quite a few pictures such as the one in this article about Sirius that give a better picture of how Orion's belt "points" to it.

Alternately, there are a number of computer programs that offer a real time views/maps of the night sky.

Also check out Google Sky.