There is a theory that you should save your best content, links and images to be at the bottom of your homepage so that people have to read all of the text before they get to it. However this relies upon the weighty assumption that you will not have lost the users interest by that point. Recent studies suggest that 80% of the time is spent by the user above the fold (the area that fits into your screen resolution), so it absolutely stands to reason that this is where you should be concentrated on to convert users into customers.
If your users are spending most of their time on a certain section of your website then this is where your call-to-actions, information and details should be. Have your primary navigation bar above the fold; make it easy for people to contact you by having your contact information above the fold; have all of your top, optimised content in the first paragraph of your text above the fold; have your logo above the fold; have your most striking imagery above the fold….I think you get the picture!
This isn’t to discount content produced below the fold. If you have optimised content and appealing web design you should be able to maintain a customer’s attention so that they scroll below the fold. Have secondary navigation, interesting facts and unique call-to-actions but remember: customers are won or lost on the information and imagery you have above the fold!