I've been teaching group exercise classes and personal training for over a decade.  One of the most common technique mistakes I see occurs in the staggered stance position.  Most of the time, you use staggered stance for one-arm rows, lunges and tricep kickbacks.

Many people will stand in staggered stance like this:

Notice my foot on my back leg.  My toes are turned out to the side.  This position puts a tremendous amount of pressure on your knee joint when you do lunges.

Ideally, your rear foot should align like this:

Your rear toes should point straight ahead.  So, all ten toes face the same direction.

When you start practicing standing in correct alignment, it will feel unatural.  It may even be harder to balance when your toes point forward.  The good news is your muscles have memory.  The more you perform exercises in staggered stance, the better you'll become at recognizing the technique.  After a month or so, it will be second nature to stand in proper aligment.