One mistake I see contestants make is not investing in themselves. For example, they spend $3K on a gorgeous gown, $500 on accessories, makeup and hair and not investing on what comes out of their mouth or what image they portray. A beautiful gown, won't win the crown. You need to do the internal work.
As a business owner, I invest in programs and business coaching every year. Why? We need someone to help guide us to the next level and pageantry is no different. The interview portion of your pageant is extremely important, if you don't practice and don't work with a coach it will show during the interview. Judges can see when you are not prepared. Make the investment in yourself, work with a coach, there are so many great ones out there!