If you really want to get into smoothie-making, I have amassed all of my smoothie knowledge into a mega wiki page:
http://catch42.pbworks.com/w/page/78032378/Protein Smoothies
The primary key to a good smoothie is a frozen banana. The banana makes it creamy and since it's frozen, that makes it cold. If you just use ice cubes, it waters it down. Using other frozen fruits helps as well, since it keeps the temperature cold.
Also, you can't just lop ingredients in & expect it to taste awesome (although that's mostly what I do, but just for protein smoothies that I chug haha) - you use smaller amounts & get a recipe dialed in the way you like it. Definitely start out with some tried & true recipes (look for ones on say Yummly that have like 4 or 5-star reviews out of hundreds of reviewers).
One thing to realize is that if you've ever had a commercially-prepared smoothie (such as Jamba Juice), they're chock full of sugar. That's not a bad thing, but don't expect to get the same results at home if you're not dumping in sugar. Ice cream, yogurt, sugar, all of that stuff makes for an excellent dessert/snack smoothie.