Growing up "smoothies" were a standard breakfast except in those days we referred to them as breakfast milkshakes. They are still a treat we like on hot summer mornings or really any time we want something cold and fruity.
There is no real recipe for our smoothies since they are catered to each drinker.
Start with frozen fruit. Our favorite has always been bananas. I have a freezer full of bananas. What I do is - when a banana has gotten to that point I know no one will eat it, I throw it in the freezer (peel and all). For me there's a lot of convinience in this. When I need to use a frozen banana, I run it under hot water for no more than 30 seconds and peel. I may need to use a butter knife to scrape all the stuff off but it doesn't take very long. Other family members, peel the banana and set it on cookie sheets to freeze and then pile them in freezer bags. My method has no freezer burnt bananas but it does mean a lot of slippery bananas falling out of the freezer when we over fill it. Either method works - it just depends on you.
You can also use any other frozen fruit. My grandmother would make them with frozen strawberries. The problem with strawberries is they are not always sweet and can make a pretty sour shake. I have used mixed berries, peaches and others but banana is what we seem to come back to.
We have a "bullet" type blender which makes everything in one serving. So I use 1-2 bananas, depending on their size and cover them with milk. Blend until smooth, you may have to stop now and again and add a little more milk to keep it smooth. Easy peasy - you have a basic smoothie. We like to add peanut butter and chocolate syrup to our banana smoothie but you can really add anything, including fresh fruit (with frozen fruit).
What I like best about this particular method is there is no added water - no ice chunks, nor is there any ice cream. The fruit acts as ice so if there are chunks - it's kind of nice. I like working my way through a piece of soft frozen banana, more than I like hitting a piece of ice. I, also, like that I have complete control of the nutrients, full serving of fruit and milk. And the best part is if they do melt, it's not a watered down version of the drink.