Assemble your collection of fruits. You won't need more than four kinds of fruit, as you won't notice the distinct tastes anyway. Think of smoothie-making as an experiment of color and taste mixing. Banana, for example, dominates in taste though not in color. Blueberries or blackberries, meanwhile, create a powerful bluish purple hue but a more subtle taste.
Combining frozen and fresh fruits is perfectly acceptable. During the winter, fresh berries are expensive; frozen berries provide almost the same taste in a fruit smoothie, and can be kept easily on hand in the freezer.
Set up the blender, and throw in the fruit that is cut in the largest pieces. If this is a frozen fruit, also add 2-3 tbspn. water or juice to ease the blending.
Set the blender to 'puree,' 'blend,' or 'liquefy,' and start pulsing. If you notice resistance, add more liquid.
Stop the blender, and add more fruits, four or five ice cubes, and 1/2 cup yogurt or milk (if desired). Stir so that a mixture of fruits is near the blades. Blend away. Note that all amounts are approximate; you can really add as much or little of each item as you would like; remember, this is an experiment!
Once you've added all the fruits and dairy, add 1-2 tbspn. protein powder if desired, stir, and blend again. The most common types of protein powders are whey, soy and egg. According to Bodybuilding.com, different powders are used for different goals, for example, muscle building or meal replacement. Whey protein is the most common supplement for individuals trying to build muscle. If your primary goal is losing fat, choose a low-carbohydrate, low-calorie protein; this will allow you to keep your current muscle mass while losing fat. If you are instead aiming to build muscle, choose a high-carbohydrate protein powder that is still low in sugar and fat. If you are using protein to help you stay full (as a meal replacement), choose a powder with medium levels of carbohydrates and calories.
Stop the blender and taste a spoonful of your creation. If it seems too thick to drink, add more ice, water, juice or milk, and blend again. If it seems too watery, add more fruit or yogurt. If one fruit taste seems too strong, add more of another fruit or add more yogurt.
Pour into a tall glass, and enjoy! You can refrigerate any leftovers, but either shake well or re-blend before drinking the extra, because the fruits will settle in the fridge.