I support all other answers, they have great tips!
Another issue that you could address the issue is the optimization of the call-to-action. This is usually the "add-to-cart"-button or any other button/link that will get the visitor one step closer to making a purchase.
You need to make sure that this button has the right size, color, design, and text. A good way to find the best button for your purpose is using A/B-Tests. There are some tools you can use for that (even Googke analytics) or you just use one type of button for 1 week and then another button for another week and compare the click rates.
Another solution could be social proof messages. Display comments of former customers or ratings. And have many pictures of smiling humans on your website ;)