If you use Magento and are finding that you aren't getting as many completed purchases as you would like, it's a good idea to look at your Magento abandoned cart reports. You can get cart abandonment reports by using any number of analytics tools, or by installing extensions such as the Magento Abandoned Cart extension that is offered via the Magento Connect service. The extension gives you information about abandoned carts and failed orders, and if the user was signed in when they abandoned their cart, then you can use the Magento Abandoned Cart settings page to set up things like automatic money off coupons, sending messages to the user to try to entice them to come back and complete the purchase.
There are many reasons why a shopper might abandon their cart. They might simply have went off to look for a voucher code then gotten distracted and forgotten to come back to complete the purchase. They might have been unable to find a money off code and decided that they don't want to pay full price. Alternatively, they might have decided that they don't want the product any more, or they may have seen something that concerned them when they were attempting to finish the purchase, and decided to leave the site because they didn't trust that it was safe to hand over financial details to. There are many potential reasons for someone to give up on a purchase. Some of the problems are easily rectified, others are more challenging. A good Magento abandoned cart extension will make it easier for you to figure out what sort of issue you are facing, and whether it is fixable with some simple tweaks to your site, or some creative marketing.
If you are losing a lot of people at the cart phase, that's probably a sign that you need to be more proactive about how your site is perceived by your users. Shoppers are becoming more aware of how potentially insecure and dangerous certain websites can be, and how easy it can be to have their credit card details stolen. This means that they are being more cautious about who they spend money with. They might trust a big retailer like Amazon, but they're less likely to trust you as a smaller retailer if they have never done business with you before. You can get around this if you can prove to them that you are trustworthy, but that will take some effort. Make sure you have a magento abandoned cart valid SSL certificate. Make sure that your payment processors are known, popular and trusted ones in your chosen country. Offer guarantees on your products, and make sure that your site is as fast and stable as possible, so that they don't end up having fears that you're not a professional outfit. These are all small things, but they will make all the difference to how well your website runs, and whether or not people will open their wallets.