I have always been one to suck in my stomach muscles and hold it for a quick ab exercise wherever I am. Turns out, I haven't been doing it quite right! Here's the best way to suck in your abs to get a flatter lower tummy. 1. Exhale, GENTLY drawing your belly button back at the same time as gently drawing your pelvic floor upwards. 2. Your abs are drawing gently inwards, but not pulling in hard. * Making a ‘Ssssss’ sound as you exhale may help you find the right deep abdominal muscles.