Retail environments like Petco may offer opportunities for friendly competition with your coworkers and other stores in your district and region. Tell the interviewer about your experience in competitive environments, whether that means racing others to achieve the highest sales, working towards a promotion, or eagerly trying to win a new contract. Show the interviewer that you rose to the challenge and that you were excited to push yourself to be the best. It is a definite plus if you have cheered on your competitors and helped them along the way. Be sure to mention any successful outcome.