Frothing milk isn't rocket science, but there are a few things to keep in mind. Always use cold, fresh milk; it froths easiest, and you have plenty of time for the milk to heat up. First, fill the milk jug to the bottom of the spout.
Next, position the steam wand at a 60-degree angle to the floor, through the nose of the milk jug, about 2 cm below the surface, and 1 cm from the wall at 3 or 9 o'clock. This ensures a circular rotation of the milk in the jug from the start.
You gently suck in the air right at the beginning, while the milk is below 38 degrees Celsius. After opening the valve, you simply need to move the milk jug downwards slightly until you hear a hissing sound. At this point, air is sucked into the milk and the milk volume increases. This process should be completed when the volume has increased by a third and the milk has reached body temperature. Only then will there be enough time to incorporate the air into a silky milk foam.
To do this, move the milk jug slightly upwards along the steam wand until the nozzle is again 2 cm below the surface. The position of the steam wand in the jug remains unchanged at 3 or 9 o'clock. Now the milk rotates without taking in any more air until it reaches 65 degrees Celsius. If you froth the milk at a higher temperature, the lactose will burn, and the milk will lose its sweetness. You'll also burn yourself while drinking it.