How to choose the best:
Spinach

Touch

Look for nice robust leaves, and avoid any leaves that seem to be wilting, soft or slimy at all.

See

The leaves should look vigorous, with a consitent, bright green color all throughout.

Avoid any leaves that seem to be going yellow or brown.

Some more details:

How to store

Spinach does best in a humid environment, so simply place a wet cloth (or paper towel) at the top of the bowl or container.

When it's in season

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.

FYI: for this Vegetable, its best to buy organic.