In a blender pour it about half full with plain yogurt.
Add 1-2 frozen bananas and enough frozen fruit to fill it 3/4 full.
Fill it up to the top with a juice of your choice and blend. I add more juice or even water to the consistency we like.
We use plain yogurt I make or buy from Costco. I choose plain so it doesn't have extra sugar in it. We put in frozen berries also from Costco. The one we buy has blueberries, raspberries and marionberries. For juice I usually use 100% juice cranberry juice or a cran/raspberry. I do this for several reasons, one being it's good for you and two being no one likes it plain so it ensures no one drinks it and leaves us unable to make smoothies! Any juice would be good though. The best part of all is older kids love messing with blenders! Caleb is our family smoothie maker lately! He makes awesome smoothies all on his own. In fact, if Addison decides she wants a smoothie she'll bring her special cup to "Buddy" (Caleb). Too cute!
I want to make note here that although I would LOVE a fancy blender someday, I have a cheapy from Meijer or something like that. It's probably as old as Carter and it still does the trick! So don't think you need a fancy smoothie maker or new blender to give it a try ;0)
Happy smoothie making!