Breathe out the air in your lungs
You can’t contract your abs fully if you still have air in your lungs. If you are on of those persons that hold your breath during abs exercises, then you are not taking advantage of full muscle contraction. Instead of holding your breath, exhale on every contraction. If you let go the air when you start the movement and stop when you have no air left in the lungs, you are using the abdominal contractions, instead of using the hip flexors and gravity.
Lower abdominal training first
Do lower abdominal training first. You can use the stomach exercise of your choice. Why? Because when you tighten the lower abs, the rest of the abs muscles also contract and stabilize to prepare the movement. So you are working the whole abs section at the same time!
Start with lower abs until you can’t do the abdominal training correctly, then work the obliques and finish with the exercises for the rectus abdominus, the center part of your abs.
Let Your Muscles Recover
Abdominals recover within seconds, unlike other muscles that need a few minutes. Because of this small recovery time, the abs are responsive to continuous movement. So this means that you have to to do exercise after exercise with few seconds of rest until you feel exhausted.