Amazon ad optimization mistakes rarely look dramatic. They show up as an ACOS that drifts up, budgets that run out by noon, or search terms nobody reviews. The most expensive ones are running auto campaigns without harvesting and negating terms, setting one ACOS target for every product, bidding without considering placement, advertising weak listings and judging results without TACOS or organic sales.
Mistake 1: are your auto campaigns running unchecked?
Automatic targeting in Sponsored Products is useful for discovery. The mistake is never reviewing what it finds. Auto campaigns match ads to search terms and products Amazon considers relevant, and some of those will never convert.
Download the search term report from the advertising console every week or two. For terms that convert well, add them as exact match keywords in a manual campaign and as negative exact in the auto campaign, so the term is managed in one place. For terms with spend and no sales over a meaningful number of clicks, add negative keywords.
How many clicks before a term is judged?
There is no universal number. A common approach is to compare clicks against your conversion rate: if a product normally converts at around 10 percent, a term with 20 to 30 clicks and no orders is worth negating. Set the rule from your own data and apply it consistently.