Learn as you go. You really can't mess these up. Even if you add the same ingredients, smoothies are different everytime you make them. Takes quite a while to get tired of them. And quite a bit better for you than a bag of chips.
Smoothies are great following a work out or a good run - lots of vitamins and protein.
Use whole milk for a higher calorie smoothie Don't be afraid of a little fat - your body needs some for rebuilding muscle. Actually hard to find in some stores. Wheat Germ - In Kroger and Foodtown, wheat germ is in the cereal isle. I like the honey flavored for smoothies. Frozen cherries, grapes, fruits with skin don't blend very well - I usually avoid them.