I started with these ingredients:
Normally I would use a fresh banana, but I had a bunch of bananas that were about to go bad, so I cut them up and froze them, and I actually like the way the smoothie turned out with the frozen bananas. That is about 2 handfuls of baby spinach, 1 small glass of water, and 1 apple cored and sliced, and about 1 banana (peeled and cut into pieces).
First you put the spinach and water in the blender. I kind of stuff the spinach down in the bottom, because I have a cheap blender, and it doesn't always get all the stuff blended smoothly. I use the liquefy option. It just takes a few seconds. Then I add the apples (usually in 2 batches - again, cheap blender). Few more seconds on liquefy. Then I add the bananas. The banana adds a creaminess. You can also add ice or more water at this point. Chris tends to like them a little thinner, so I added some more water.
And then you get this:
Yes it is green, yes it looks a little bizarre. But I can tell you that I can't taste the spinach. The banana and the apple provide almost all of the flavor. And I don't know what exactly it is, but I have some much more energy during the day after I have one of these. Chris is even a believer (mostly - he still thinks it is a blog fad, but he agrees that they really work). There are tons of combinations out there. The other ones that I have tried are kale instead of spinach and rainbow chard instead of spinach. I've also added frozen berries instead of the apple. But then they are purple smoothies. :) The kale and rainbow chard combos had a different flavor (and texture), and I think I will have to work my way up to those over time. I think I need a better blender to try kale again. It didn't liquefy as well.
The place where I first learned about green smoothies was Happy Foody. She has some great ideas (and inspiration) and even a link to a video on how to make them. Just google Green Smoothie, and you will find a ton of resources. Particularly on peoples blogs. If you try one, let me know!