Fallouts are essentially the same as ab wheel rollouts, only using suspension straps instead of a wheel. The nice thing about fallouts is they can be easily regressed and progressed depending on your current level.
Start by doing them standing on your feet. The shorter your set the straps, the easier it'll be. The longer the straps, the harder it'll be. Start with the straps at about waist height and lengthen them as you improve.
Where you stand in relation to the anchor point will also affect the difficulty significantly. Standing in front of the anchor point will make it easier, while walking back underneath the anchor point will make it harder.
The next step is to try them starting from push-up position as shown here. These suck, in an awesome way. You can also elevate your feet.