Salt has a remarkable capacity for bringing flavors together. This is true both in savory foods as well as sweet. I always add a pinch of salt to each smoothie I make. When I forget to add salt, the difference in flavor is quite noticeable. Make sure that you're using a good quality sea salt that will contribute to your overall health, rather than deplete it.
I always add a half of a vanilla bean to every smoothie I make. It really adds to the flavor of fruit smoothies and green smoothies alike. I use the whole vanilla pod which gets pulverized in the VitaMix. If you don't have a high-speed blender you can split the vanilla pod down the middle and scrape out the seeds with the back of your knife. I think this is better than using vanilla extract, which always leaves an alcoholic taste to me.
Some feel that vanilla is cost prohibitive. I generally buy my vanilla beans from Fairway here in NYC where it costs $2.99 for two beans (that's 4 smoothies). For those of you outside of New York, i've heard that Costco now carries vanilla beans. There might be less expensive resources online. If you find any, please let me know.
Update: Antony Heaven of livingrawfooduk.blogspot.com just emailed me a fantastic site where he buys his vanilla beans from. organic-vanilla.com. Their prices are FAR better than anything i've seen AND they're organic. Just placed an order of 30 beans for $10. Thanks Antony!
3. Coconut Water:
Nothing tastes better to me than when I use coconut water as the liquid in my smoothies. It's always strange to me because coconut water isn't that distinct from filtered tap water to me. But using filtered tap water in my smoothies always makes them taste quite bland. Also, coconut water has copious amounts of electrolytes, which is why it is often referred to as "nature's Gatorade."
4. Cleaning the Blender:
Many have told me that the task of cleaning their blender is SO daunting that it puts them off of making smoothies. They are generally quite excited to learn my method for cleaning (I honestly have no clue where I learned it). Simply fill the pitcher 3/4 of the way up with warm water. Add 4 to 5 drops of dish detergent (phosphate free, naturally) and give it a whir. The power of the blender should remove any schmutz that accumulated on the sides. Give it a rinse and turn it upside down on a dish cloth to dry. It's honestly one of the easiest things to clean in the entire kitchen.