One of the most basic moves in ballet is a plié. A plié is a bending of the knees, done in any of the five positions of the feet. There are two types of plies: demi plié and grande plié. Those words mean "small bend" and "big bend," respectively.
If you'd like to see demonstrations of the concepts in this post, watch the video version here!
Beginner
To do a demi plié, stand in any of the five positions and bend the knees as much as you can with your heels remaining on the floor.
A grande plié is a deep knee bend. The heels have to come off the floor in a grande plié, except in 2nd position, but you want to resist it as much as possible.
As you descend into a plié, imagine you're a slice of bread in a toaster. Keep your torso upright and your bottom underneath you, or else you'll burn yourself on the sides of the toaster!
Don't burn your knees on the toaster, either. It's important to keep your knees pointing out to the sides of the room, directly in line over the toes. Not only does it look nicer, it also prevents injury by minimizing torsion in the knee. This is especially important to remember in 4th and 5th position, where maintaining turnout is more difficult.
The basic, classical arm movement accompanying a demi plié is to bring the arm from 2nd to 1st when you bend your knees, then back to 2nd when you straighten. Grande plié arms make a semicircle: lower the arm to en bas, up to 1st, then back to 2nd.
Musically, demi pliés typically take two counts. Grande pliés take four.
Beginner/Intermediate
In a grande plié, you don't want to"sit" on your heels. It makes it much more difficult to come back up. Keep the base of your pelvis above your knees.
A common mistake I see in beginners is shoving the heels forward to increase turnout. It's easy to be tempted, since your turnout range increases in the plié position, but forcing your turnout is bad for your knees. We like our knees. Please be nice to them!
When doing two demi pliés in a row, you will typically use the grande plié arm motion. On the first demi plié, the arm lowers to en bas. On the second, when you bend, the arm lifts to first position, then opens to 2nd as you straighten.
When doing two grande pliés in a row, it's common to reverse the arm on the second grande plié. To reverse the arm, lift it to en haut, lower it through first to en bas, then raise it back up to 2nd.
Your head follows the hand as it moves. If it helps, put a sticker on your palm to remind you where to look!
Intermediate
Now that you've got the arm and leg motions down, it's time to coordinate them with the music more precisely. For both the arms and the legs, it takes one count to get to each position.
(There's one exception: regular grande plié arms only move through three positions--en bas, then 1st, then 2nd--but there are four counts! To compensate, lowering the arm to en bas takes two counts instead of one.)
For a more polished look, try to have your arms and legs arrive in their positions at the same time.
Use every count in the music. You never want to find yourself sitting at the top or bottom of a plié, waiting for the music to catch up. In fact, try to be almost late! The same goes for the arms. The result should be a smooth, fluid movement with no stagnant moments.
Intermediate/Advanced
Your turnout initiates a plié. The motion of your inner thighs rotating forward is what causes your knees to bend. When you straighten, find that same feeling of rotation on the way up.
Keep in mind the toaster analogy from when you were a beginner. You're still in the toaster! In fact, now imagine you're in an even narrower toaster! Even in intermediate dancers, it's common to see chests collapsing forward or bottoms sticking out a little bit. Take care not to overcompensate by tucking the hips or arching the back, though. Keep your back as straight as possible.
Advanced
What really takes your pliés to the next level is adding a feeling of resistance. Feel like you're doing a push-up with your legs, resisting gravity. (My teacher once had us do a few push-ups before pliés for precisely this reason). Not only does it make the plié look more dynamic, it helps build strength and control for jumps, pointework, and pretty much any move involving a plié or fondu (which is most of them).
Lastly, use your breath! Informing your movements with your breath helps make pliés more fluid and musical, and adds a gorgeous touch of artistry.
Keep up the good work! And if you have questions, let me know in the comments and I'll get back to you.
-AJ