Opening an online store is easy. Making one that sells is a different job. The mistakes below are not rare; they are the ones we meet most often when a store is handed to us to fix, and each of them was cheap to avoid at the start.
Decisions at setup
The first mistake is choosing the platform before the business model is clear. A subscription product, a dealer price list and a single product store do not need the same system. Choosing the tool first turns the business into whatever the tool allows.
The second is treating integrations as a later problem. Payment, shipping, invoicing and accounting are what turn an order into a shipped box. Left to the end, they are the reason a launch slips by months.
The third is building the product page as a catalogue entry. A product page is not a record; it is where a decision is made. Contents, size, delivery time and return terms belong on it, because a question left unanswered is answered by closing the tab.
The path to payment
The fourth mistake is the length of that path. Every extra step between basket and payment raises abandonment. Forced sign up, shipping cost revealed at the last step and a form that does not work on a phone are the three that cost the most.
The fifth is not measuring where people leave. Listing, product page, basket and payment should be measured separately. Without that, improvement is guesswork and every change is an opinion.
It is not the storefront that sells, but the distance between the product page and the payment screen.
After the opening
The sixth mistake is launching without conversion tracking and then buying advertising. Money spent in that period cannot be judged afterwards. Tracking is not a reporting nicety; it is what makes the spend readable.
The seventh is building nothing for the second order. Acquiring a customer is the expensive part; the second order arrives without paying it again. A consumption estimate, a reorder reminder or a simple returning customer flow changes the economics of the whole store.
None of these seven are difficult. They are simply decisions that have to be made at the start, when they are still cheap. If you want to go through your own store against this list, we can look at it together.