It’s easy enough to start a lemongrass plant: get one here, or buy fresh stalks in the produce section, set them in a glass of water, and wait a few weeks for them to take root. Give the plant rich soil amended with plenty of compost, a good granular, balanced organic fertilizer, full sun, and as much heat as you can provide. Plan on watering it with a nitrogen fertilizer every few weeks throughout the growing season. (I use a mixture of fish emulsion and kelp meal.)
You can also grow lemongrass in a container, which makes it easier to shelter in the winter. The plants do well in a greenhouse but aren’t suitable as houseplants because they won’t get enough light indoors, even in a sunny window.
If you are lucky enough to have a healthy plant growing in the ground, dig out a 6 inch chunk of roots and stalks before winter comes and bring it indoors in a pot. It will stay fairly dormant, but it will get through the winter and you can plant it outside again in the late spring.
Harvest lemongrass by reaching down to the base of the stalk and giving it a firm twist and pull. Muddle the tender stalks into rum, vodka, and gin drinks to give them a more interesting and complex citrus flavor.