Ensure your checkout process is streamlined. Offer as may reputable payment providers as possible. Offer free shipping. Check your pricing compare to your competitors. Abandoned cart email flow. Don’t require your customer to create accounts a checkout. Make pricing and shipping clear up front. Perhaps “sticky cart” features to emphasize items are in cart, this is probably frowned upon here, but definitely helped out conversion rate. I’m sure there are others I’m forgetting.

Also are you getting lots of abandoned carts? Or abandoned checkouts too? Another good trick is to use google analytics and check to see where your sessions are dropping off.