The first desmarche right: you will have just done a pair of simples, right and left, so your right foot will be hanging in the air in front of your left foot. 1 - put your right toes down immediately behind your left foot (just tuck it behind, don't take a big step backwards); 2-3 rise slowly onto your toes (weight on both feet), and turn your torso somewhat towards your partner (women will have to twist a bit here); 4-6 slowly lower your heels, while bending your torso a little towards your partner (bend from the hips, and keep looking at your partner).
The desmarche left: your will have just done a desmarche right, so your right foot will be tucked behind your left. 1 - put your left toes down immediately behind your right foot, 2-3 rise slowly onto your toes, turning your torso somewhat towards your partner (men will have to twist a bit this time); 4-6 slowly lower your heels, while bending towards your partner a little, as above.
The third desmarche: is on the right, and is just like the first, except that you start with your weight on both feet. Tuck the right foot behind the left, rise and fall and bend just as before. When you lower your heels, make sure most of your weight goes onto your right foot, so that your left is free to move in the branle.
Reverences: you begin and end these dances with a desmarche right, followed by a branle - just be especially careful to acknowledge your partner in these, inclining your body towards them, and maintaining eye-contact. There is no need for extra reverences.