Google adds on your site may generate revenue for you but may cost you sales.
You may want to get a recognized security clearance people recognize like virgin sign.
Added payment methods like paypal stormpay.
Your shopping cart makes people sign up with e-mail before checkout this could deter some people.
Other then this you must look at sheer volume
Are you currently getting about 2% leading to sales more less .
You may need to permute your site to increase it’s sales.