What's the rule on eye contact?

It depends on the day - If I am open for conversation with that person then I will look that person in eye. If I would like to avoid any potential contact with the person, I look straight ahead or glance around. I dont personally look at people in the eye unless I am about to approach them; having said that, it happens when I am walking down the street from time to time - just glance for a sec tho, anything more is creepyish. Also, if you are working working in customer service it is very important to understand the art of eye contact and conversation.