I used to get frustrated seeing all the "green" seats blocked off on the map. I realized the best way to get preferred seats (like those closer to the front) is to join AAdvantage—even without status. Often, seats that are "Preferred" just cost a small fee, but if you wait until check-in, they sometimes open up for everyone. On my last flight to CLT, I snagged an aisle in row 8 just by checking the app the moment the check-in window opened.