Seb7 - 12:30 pm on Feb 11, 2009 (gmt 0)

I'm probably repeating some advice already given, but heres my take:

You need lots of relevant visitor traffic. A 1% conversation on all website traffic is quite the norm.

Use things like Google Analytics to see where you current visitors are coming from. Use conversation monitoring to see where your current buyers are from.

SEO the website to target the audience which is most likely to buy your product, and focus the website on given your potential buyers what they most want.

Setup or tweak an adwords account to get lots of targeted visitors - and use the adwords conversation monitoring tools - as this will tell you which adverts are making you money.