How do you figure out the lewis dot structure for a molecule like water?

and how do you figure out the lewis dot structure for a polyatomic ion like Sulfate?How do you figure out the lewis dot structure for a molecule like water?
Without some way to show the lewis structure it's hard to explain how to draw lewis dot structures.





However. Theres this really excellent website step by step animation of how to draw lewis dot structures. But you need shockwave player to be able to use it.





http://www.kentchemistry.com/links/bondi鈥?/a>