SIT UPS?--NEWBY TO THIS FORUM

IVE BEEN GOING TO THE GYM FROM QUITE SOME TIME, I WAS CURIOUS IS SIT UPS THE BEST THING TO DO FOR OUR BELLIES? I HAVE  LOST A LITTLE BIT IN MY STOMACH..BUT THE REST OF MY BODY IS TINY AND I KNOW SOMETIMES THE BELLY IT THE LAST TO GO IS THERE ANYWAY TO KICKSTART THE TUM TUM? THANKS

I don't know what they are formally called but:  use the dip bar to hold yourself up, arms straight, and bring both knees together slowly up to waist height and back down; 12 to 15 per set,.... really burns the ole abs.  Leg lifts also work the lower abs if that an area of issue.