Get a coupon for free game play
Many of the coupon books/flyers available everywhere on I-Drive have a "Buy $10 get $10" or "Buy $20 get $20" coupon which doubles your game credits. Also, unlike most other D+B locations, these coupons are still accepted on Wednesdays, where all games are already half price - essentially quadrupling your game play. If you have multiple kids, bring multiple coupons as they'll usually honor one for each game card you fill.