One sure sign of spring is fresh asparagus in the produce aisle. Fat or thin; green, purple, or white; the keys to delicious asparagus are freshness and proper preparation. The plant brings a delicately bright flavor, and notes of subtle acidity, to any dish.In Season: Asparagus is at its peak from February through June, though hothouse asparagus is available year-round in some areas.What to Look For: Thickness is a matter of taste. Choose bunches with tightly closed tips and no flowering. Stalks should be bright green and firm (or pale ivory for white asparagus).How to Store: Asparagus is best cooked the day it's purchased, but it can be kept in the refrigerator for up to five days in one of the following ways: Wrap the bottoms of the stalks in a damp paper towel and place in a paper bag; store in crisper. Or stand the bundled stalks in a bowl with about an inch of water.