Good basic form on Romanian Deadlift (RDL).

For the lunge, you simple step one foot forward and lower your body down until your rear knee is touching/nearly touching the ground, then you push off and step forward with the rear leg.  Remember to keep your head and torso aligned.  The hands can be clasped behind the head or on the hips.  This exercise can also be done with dumbbells and kettlebells, etc.

 

This is the same as a regular lunge except you will step to the side.  You can also use dumbbells or kettlebells, incorporate a step-up with a bench or box, or throw a jump into it--whatever.     

Bring your knees as close to your chest as possible.  This is just a two-legged variation of the Mountain Climber. 

The Iron Mike can also be done while holding dumbbells or kettlebells.  The hands can either be placed on the hips or clasped behind the head.  It is important to keep the head and torso aligned. 

These are also commonly referred to as "single leg squats", however we at Fatal Fitness differentiate these between two exercises.  So the video above depicts the pistol.  Some key points to remember--your heel should remain planted throughout the entire thing.  This is perhaps the most important point.  Sit all the way down--your butt should touch your calves.  Pause at the bottom, DO NOT BOUNCE.  Finally, drive your heel into the ground to return to the starting position.