[S Starr]

I eyeball too, but I've had success with carrots, broccoli, and cabbage in fruit smoothies. (!) I typically go heavy on strawberries since they're so low calorie. I also like frozen blueberries and frozen banana to make the texture thick. (You could also add frozen milk or yogurt cubes.) When my mom makes smoothies in her vitamix, she adds flax seed, but most blenders can't make the seeds into powder -- but you could add powder. Good fiber and omega whichever-it-is as long as the powder is relatively fresh. And if your fruits aren't sweet, I would add some OJ or apple juice or jam.