This tried-and-true ab exercise will target all your abdominal muscles.
Start on the floor resting on your forearms and knees.
Step your feet out one at a time, coming into a plank position.
Contract your abs to prevent your booty from sticking up or sinking. Your spine should be parallel to the floor, with your abs pulling toward the ceiling.
Hold 30 seconds and work your way up to one minute, as you get stronger.