White asparagus is asparagus that has not been in the sun. It is not able to photosynthesize which would turn the spears green.
Look for firm, straight stalks with closed tips. Stalks should not be limp or be dry at the bottom of the stalk. To store, wrap the bottom of the asparagus in a paper towel. Put it in a plastic bag and refrigerate. It can last up to 4 days.
Asparagus should have the bottom of the stalks cut off. The end is very fibrous. The asparagus should be gently washed. Asparagus is very solid so it does well on the grill. You can also roast them in the oven with a bit of olive oil, black pepper, and sea salt.