I apologize to all my readers to whom the excerpt below is gobbledygook, but it is brilliant gobbledygook! I think all web sites should be designed according to this approach. I intend to apply it myself.

Bryan Eisenberg in his column at ClickZ:

Dissect the buying process into component parts for each persona, then measure those micro conversions in the clickstream. Not only can you better understand how well you’re persuading, you can also segment conversion rates by persona. That allows you to focus on cumulative conversion rates for the site, instead of simply an average conversion rate.

Most sites must plan for many more factors before a visitor will even participate in the conversion process. Some factors can be planned for, some can be influenced, and some are outside our control.

To begin calculating what your conversion rate should be, work backwards from the 100 percent conversion goal. Don’t begin with your currently miniscule conversion rate and find ways to increase it. The result will be a site optimized for a homogenized few.