Purchase lemongrass with stalks that are full and firm with a pale green color. The lemongrass should be moist to the touch, with a fragrant aroma. The bottom of the stalk shouldn't be woody and tough.
Wash the lemongrass under cool, running water. Trim the ends of the lemongrass and peel off the outer leaves. Use a sharp knife, as the lemongrass is fibrous and can be difficult to cut. Use only the bottom 4 to 6 inches of the stalk and discard the grass as it is too tough to use in cooking. Or you can save the grass for potpourri or tea.
Place the lemongrass stalk on a cutting board and crush it with a kitchen mallet. Alternatively, pound it with a mortar and pestle. Cut the crushed lemongrass into large chunks.
Add the crushed lemongrass to your dish, and then remove it just before serving as the lemongrass stalk is tough and difficult to chew. Alternatively, chop the tender inner part of the lemongrass stalk very finely and add it to the dish.
Place unused lemongrass in a plastic bag or airtight container. Store the lemongrass in the vegetable bin in your refrigerator.