Hi Ali!
I can share some tips with you in regards to improving conversion rates and, correspondingly, decreasing cart abandonment rates.
From my experience delivering and then supporting various shops, what matters to the end user is if they feel safe and secure on the website, completing the transaction. Naturally, the product (service?) and price matter a lot. But also if they feel their card details are safe, if they feel they will receive their goods from you. And of course the checkout process should be relatively simple and straight forward.
So, providing your products have good pictures and descriptions, providing the price is competitive, and providing you are not scaring them with unexpected fees (like shipping fee which some of the consumers may think is too high), you should look at the design, the look and feel of the shopping cart and checkout process.
It should be made very clear how to proceed to checkout from the shopping cart. It should be made clear (ideally) how much they will pay for delivery. It should be made clear that their data is safe with you. They like to see which payment methods are supported.
Next is the checkout. Make sure you don't ask for things you don't really need (like date of birth, for example). Some sites have a so called "one page checkout". Other sites prefer to have multiple pages, one per each set of questions (like contact details, shipping, billing addresses, etc). Experiment with those to find out which is your users' favourite.
My experience tells me the checkout (and shopping cart) should be free of various banners. Some of my clients even ask to completely remove all the design framework, leaving plain "black and white" design, to allow customers concentrate on the process.
Naturally make sure the SSL (https) is installed - makes people feel safe, even if they don't put their card details on your site.
Also, note that most of the Ecommerce solutions store cart contents in the DB for customers. So try chasing after abandoned carts, offer them some discount (if your margin is good) and see how they come back to complete their purchase. Use this opportunity to ask them why they didn't complete their purchase the first time. Experiment with price and especially shipping price - it seems to affect decisions sometimes.
Let me know if this helps, or if you have more questions. Cheers!