The ski squat sneaks up on you like a ninja. You'll think it's easy at first, but you'll think again by the end of it.
Place your feet shoulder-width apart, about two feet out from the wall, and lean your back against the wall. Bend your knees to a slight partial-squat position. This is position one.
After 10 seconds, lower down to position two, about two inches lower.
After 10 more seconds, lower another two inches down to position three. Your thighs should be about parallel now.
Drop down twice more, with the last position being about as far as you can bend at the knees: "ass to grass."
Most people are quivering lumps of Jell-O by this point. If you're not:
Extend each static position to 20 seconds
Do it one leg at a time
Hold a dumbbell
Come back UP two inches at a time after you work your way down the wall.
Can you smell that? That's lactic acid seeping from your pores.