Be in pointe shoes as much as you can. Once you've gone beyond beginning pointe work, wearing the shoes for barre work is a good habit.
The sole of the foot, and ankle, have to work so much more with every tendu, degage, and rise onto demi-pointe. The shoe resists, and the muscles get a better workout.
If the thickness of the sole makes your foot wobble because it does lie flat on the floor, use a wood file, and shave the sole down lightly. You can get the sole close to flush with the satin, so that your foot will be flatter on the floor. Straining the ankles from wobbling is distracting, during ballet barre work.
Even wearing worn out pointe shoes is better than wearing soft shoes. There is still more effort needed, until the shoe is completely mushy.
If you're still pre-pointe, or an adult ballet beginner, here's some tips to help you gain from using the ballet barre properly:
*** understand correct weight placement on your feet (or supporting foot) which is, evenly distributed between the center of the heel, the area at the little toe joint at the outside of the foot, and the area at the big toe joint at the ball of the foot.
*** check frequently during barre work, by lifting your hand off the barre, that your weight has not moved back onto the heel.
*** additionally, at frequent opportunities, see if you can lift the heel of the supporting foot, and place back down, indicating that you are not back on your heel.
These two simple points show you how to use the ballet barre to improve your balance and strengthen your ballet technique.To get into pointe shoes faster, learn more about better ballet technique, and ballet positions.