Do you analyze keywords your visitors type in their search bars?
Do you use google analytics to find out what keywords are being searched and how well they convert?
Do you sort keywords by conversion rate which drive the most traffic and buyers? Use google analytics.
Do you make sure keywords surfers use to get to your site are the best match to your content?
Do you have 10-15% off discounts available on rotating basis? Try either monthly or seasonal specials.
Do you allow subscribers to register to your newsletter or RSS feed?
Do you use robust affiliate software?
Do you track affiliate sales?
Do you analyze the computer specificiations of your visitors? Use google analytics to find out?
Do you submit to free/paid directories?
Do you use google website optimizer? Google has just released a powerful tool that allows you to test changes to your website and will tell you which changes brought in the most customers.
If your website conversion rate doubled, did you know your cost-per-acquisition would be cut in half? http://www.paloalto.com/common/calculators/conversionrate.cfm