Use a frozen banana as the base
Add chilled milk or a milk alternative
Include yogurt or Greek yogurt for thickness
Add peanut butter, almond butter, or another nut butter
Blend in oats for a thicker texture
Use frozen fruit instead of fresh fruit
Add a few ice cubes if needed
Use less liquid to keep it thick
Blend until smooth and creamy
Let the shake sit in the freezer for a few minutes before serving