What to look for: Well colored (light green or a darker shade of green color) firm compact sprouts. The ideal Brussels Sprout is not less than an inch in diameter and no longer than 2 ¾ inches.
Now I don't expect you to go shopping with a ruler or a ring sizer, but this gives you an idea of the approximate size that will pack the most nutrients and of course flavor!
What to Avoid: sprouts that have been trimmed down too far or starting to yellow. Also look for black spots on the tips of the leaves or larger sprouts that have burst ( a split in them) open or are puffy and light in weight. All are signs of sprouts that have been around too long or are better suited for cattle feed.
All about Brussels Sprouts
Adult Style Brussels Sprouts
Brussels Sprouts with Pancetta