How to spot a fake Rolex

First, here are few hints on how to spot a fake Rolex from Yahoo answers:
  1. On a submariner turn the bezel. It should turn smoothly, and not make an audible “click” sound. The steps are ½ second, not one second like a fake.
  2. Almost all fake Rolex have a smooth moving second hand. You can not see the difference without a microscope, so ignore any reference to a “sweep” second hand. The word “sweep” in watch terminology has nothing to do with how smooth the hand moves. 
  3. Shake the watch gently from side to side. If you can feel and hear the weight inside the watch scraping on the inside of the watch, it is fake. A real Rolex is perfectly balanced. You can not feel or hear the weight moving.
  4. A magnet will likely stick to the bracelet of a fake Rolex. The bracelet of a real Rolex will not react to a magnet.
Check out also this article.

In addition, here are few videos that will give some basic knowledge on how to spot a fake Rolex watch: