There's a reason this tender herb is so widely used around the world in Asian, Latin American, and Indian cuisines—it has the magical effect of brightening other flavors, cutting through richness, and cooling spicy heat when combined with other flavors in hundreds of ways. Cilantro pairs well with garlic, lemon, lime, chiles, and onions, and with other herbs like basil and mint. Don't bother with dried cilantro; it has very little flavor and cannot be used interchangeably with fresh.
Parsley can add a fresh herbal note in cilantro's place, but you won't get cilantro's unique flavor.
Look for perky and fragrant bunches. Avoid those with leaves that are wilted, yellow, or blackened.
Wash cilantro well in a few changes of water as it can be quite sandy. Dry it well, preferably in a spinner. When preparing cilantro for chopping, you don't necessarily have to remove all of the stems. Cilantro stems are quite flavorful, so if they're thin and tender-crisp (bite one to check), just chop them up along with the leaves.
To keep herbs at their freshest best, treat them like a bouquet of flowers: stems down in a few inches of water. Keep the bouquet loosely tented with a plastic produce bag and store in the refrigerator and your cilantro can last up to 2 weeks. Otherwise, keep cilantro in the crisper drawer in the refrigerator.