Gender determination

Darleen • God first! Due with a beautiful baby girl September 30th, 2015! So in love already!👨‍👩‍👧
Does anyone have any tips on what I can do to make sure we find out gender at our 20 week ultrasound next week? I'd be so dissapointed if we didn't find out, so I want to MAKE SURE that we do! (: thanks!