When making a bottle, always wash your hands first. It is important that you use the right amount of powder. You use one graduated measure in 30 ml of water, two in 60 ml of water and three in 90 ml of water. Then roll the bottle between your hands to avoid clumps. You can warm it up in a bottle warmer or microwave. When warm, shake the bottle and check the temperature of the milk on the inside of your wrist.
In the video below, the midwife shows you all of the steps (in dutch).