One-word cues work better than two-word cues. Two-word cues work better than three-word cues, and so on. Simplify, simplify whenever possible.
"Wiggle" - get the weight off the balls of the feet by wiggling the toes.
"Eyes" - get the head up and the eyes focused forward not down.
"Sit" - send the hips back in the squat.
"Chest" - big chest
"Tall" - lengthen the spine as long and tall as possible
"Tight" - firm up the core and everything else while you're at it.
Also, visual imagery works better than technical descriptions.
"Imagine trying to touch your butt to the wall behind you" works better than "Make this a hip-flexion movement with the center of gravity on the heels."
"Make a big chest like you are at the beach and a pretty girl walks by" gets better results than "Depress your shoulders, elongate your spine and elevate your sternum."
A good book on the subject is "Dynamic Alignment Through Imagery" by Franklin.