Use a ripe banana for natural sweetness and a smoother texture. Underripe bananas can make the smoothie taste slightly starchy.
Blend for longer than you think you need. Cottage cheese needs a bit of extra time to fully break down and become silky smooth and you don't want to see any of the curds.
Frozen berries work really well and make the smoothie thicker without needing ice, which can dilute the flavour. You could add ice if you prefer.
If your blender struggles, add the milk first, then the cottage cheese, and softer ingredients before the frozen fruit. This helps everything blend more easily.