For the record, these aren't completely like Jamba Juice. I am also ripping off V8.
General guideline is that you want about a 1:1 balance of fruit to vegetables, something juicy enough to make it drinkable (or add water), and something other than fruit or veggies to give it flavor (in addition to the spices listed below, I've also tried peanut butter). If the fruit doesn't give it enough sweetness on its own, add honey or agave nectar.
Venergy Drink 1 (aka V8*)
1 grapefruit
1/2 cucumber
2 carrots, peeled
3-4 handfuls of blueberries
1-2 handfuls of grapes
1 inch piece of scallion
1 tsp ground ginger
2 sprigs of fresh parsley
1 tsp of honey
Venergy Drink 2 (aka V12 - pictured above)
1 peach, pitted
1 large orange
2 carrots, peeled
1/2 cucumber
3-4 handfuls of blueberries
1-2 handfuls of grapes
1/4 cup of salad (mixed greens, cabbage, chard, lettuce, etc)
1/4 cup of broccoli
1 tsp cinammon
* I am using the apparent V8 definition of what constitutes a vegetable, as their recipe includes the herbs parsley and watercress, as well as tomatoes - which, despite what the Supreme Court might tell you, are a fruit.