Garlic chives, Allium tuberosum, are among my favorite herbs. They grow well in my garden and are useful in many dishes. In late summer to fall they also produce clusters of white, star shaped flowers which make tasty garnishes for soups and salads.
Garlic chives are hardy in zones 3-9 and grow best in a sunny site with rich, moist soil. However, they are tolerant and can grow successfully in less than ideal conditions. Mine grow through most of the year, but in colder climates they will go dormant. Mulching will ensure an early start in the spring. Be aware they spread by underground rhizomes and can become invasive. To avoid this, you can grow them easily in a pot. I learned this the hard way, as they are encroaching into the dianthus that grows next to them in the herb bed. I plan to dig mine up this fall and replant in plastic pots, which I will bury in the ground. It is also important to cut off the flower heads before they set seed. Otherwise, next year you may have them sprouting in other parts of your garden.
I actually have garlic chives growing in two areas. The first is the herb bed, where I have four groups centered around a bird house. 
Garlic chives grow to about twenty inches and have flat leaves, unlike the more common onion chives, which have hollow, tubular leaves. Harvest the leaves by pinching off close to the ground. Fresh is best, but they may be frozen if necessary. Drying is not recommended, as they lose their flavor when dried. Rich in vitamin C, calcium, and iron, garlic chives are great added to any dish enhanced by onion flavor, including meats, herb butters, starchy vegetables, and egg and cheese dishes. They have a more robust flavor than onion chives, and with a hint of garlic, so use sparingly until you determine how much is to your taste. Add garlic chives during the last five to ten minutes of cooking, because heat will destroy the flavor.
A hint to get rid of garlic breath: chew some fresh sweet basil leaves. It works!