Uddiyana bandha can be practiced alone or in conjunction with mula bandha. To engage this bandha, sit in a comfortable cross legged position. Exhale your breath, then take a false inhale (draw the abdomen in and up without taking in any breath.) Draw the belly up underneath the rib cage. To release, soften the abdomen and inhale.
Uddiyana bandha tones, massages and cleans the abdominal organs. If you are familiar with mula bandha, you will see that the drawing up of the pelvic floor naturally leads into the drawing up of the abdomen. This is how the bandhas work together.