Squat: keep your belly and butt tight and knees out as you squat
Situps: Stay tall through the spine. Try the butterfly or straight legged variations for a challenge
Lunge: Keep your hips square and forward, feet shoulder width apart and front shin vertical
Pushup: Screw those hands in and tilt shoulders forward as you drop all the way to the ground.
Burpee: For an extra challenge try jumping in and out with your heels and big toes together and your heels always on the ground.
Squat Jumps: think explosive in the hips, landing with most of your weight on your heels
Hollow Rocks:Keep your legs around a 45 degree angle and modify this workout by starting with one leg or holding the hollow position, keeping your lower back pressed into the ground
Arch Rocks:reverse of hollow rock, press your hips into the ground, butt squeezed