What Should You Consider Before Building an Online Store?

I recently helped a friend prepare his small business for online sales, and we discovered that there were many technical details to sort out before development could begin. While researching an ecommerce web development company dubai, we started discussing product management, payment options, inventory tracking, mobile usability, and checkout. We’re trying to keep the first version practical without making it too basic for future growth. One thing that helped was mapping out how a customer would browse and place an order. For anyone who has built an ecommerce website, what part of the planning process deserves the most attention?