One of the most frustrating experiences I have felt is seeing your site get lots of traffic and no conversions.
The reality is that from the start, your website needs to be built to convert. You need to create pages that build trust and reduce doubt. Ken Envoy calls this preselling.
We should not try to force our visitors to buy immediately.
I always try to look at my sites from the customer’s perspective. I even ask friends to tell me why they wouldn’t buy what I offer and I modify the site to improve the odds of people buying.
A professional design, professional copy, and a fast responsive website helps, but ultimately there needs to be a reason for the visitor to buy from you and not from your competitor; but more importantly to buy from you now, before he forgets about your site.
In the worst case you want to offer a newsletter or RSS subscription to maintain a line of communication that you can use later.