What is the most important factor in determining your ad position

Site links influence what Google calls "expected click through rate" (CTR), an important factor when calculating Quality Score. The more shoppers that click on your ad, the more relevant and customer friendly you seem to Google, which increases your Quality Score.!

Your bid is how much you're willing to pay on specific keywords, which your advertising provider Opens a New Window.  will determine based on your overall investment as well as your sales strategy (i.e. bidding higher on your best sellers vs. your stales). They should, however, also be helping you on that first part of the equation, Quality Score, to ensure you have a high ranking.