You can find fresh lemongrass in most Asian food and grocery stores. It is usually located with the other fresh produce, and is often sold in bundles of 2 or 3 stalks. When buying fresh lemongrass:
Look for stalks that are fragrant, tightly formed, and of a lemony-green color on the lower stalk (near the bulb), then turning to a truer green at the end of the stalk.
Avoid purchasing stalks that are loose and coming apart as well as stalks that are brown and crusty or crumbling. These are old and probably not that fragrant or nutritious any longer.
Tip: If you can't find lemongrass with the fresh produce, check the freezer section. Because lemongrass freezes well, it is often sold in frozen packets of about 6-8 stalks.