2 to 2 1/2 cups cubed soft fruit, fresh or frozen, or a combination
1 cup of liquid, usually juice or milk
1/2 cup of yogurt
1/2 cup to 1 cup ice (unless you are using all frozen fruit)
a teaspoon or two of sugar, honey, agave or another sweetener
I usually just use whatever fruits I have on hand - usually some overly ripe bananas, plus some pineapple, and maybe some leftover coconut milk, if I have some, or a few drops of coconut flavor. If it is excessively sweet (bananas get that way!), I put some unsweetened yogurt in it. I blend it on low speed, in the Vitamix, then add some chia seeds, and let them gel for several minutes. Then I blend it on high, until the chia seeds are not really visible. Then I pour some into a container, to refrigerate, for later (or a friend visiting!), then drop a bunch of ice into the VM, and blend on high (maybe adding more ice), until ice is totally ground up. This is a frequent desert, in the summertime, using the refrigerated extra for a later smoothie or two. I can't think of the last time I had to add any sweetener.
I make very simple smoothies, and they are probably not very healthy. However, my family and I love them so I will still make them! The main ingredient is banana. Banana is the basis of my smoothies, and it has always been I also add milk. The rest is according to mood and availability in the refrigerator! I like to add kiwi, strawberries, raspberries, grapes. I add all the ingredients by eye. Happy smoothie!