Step 1: start with an automatic campaign
An automatic campaign lets Amazon pick the targets while you gather data on what shoppers actually search. Set a daily budget you are comfortable testing with and a starting bid near Amazon's suggested range.
Step 2: let it run, then read the search terms
After a week or two, open the search-term report. The terms that converted are your manual-keyword candidates; the ones that spent without selling become negative keywords.
Step 3: build manual campaigns
Move proven search terms into a manual campaign as keywords, grouped tightly so one bid fits each ad group. This is where you get real control over bids and ACoS.
Step 4: keep it tuned (or automate it)
From here the work is ongoing: trim losers, fund winners, add negatives, tune dayparting. AIAdKing does this nightly so a new seller does not have to learn every lever at once — with a plain-English reason for each change.