Lo mein is a Chinese noodle dish made from boiled wheat noodles which are tossed with stir fried vegetables, meats, and a sauce. This dish is extremely popular at Chinese restaurants all over the world, and a wide variety of recipes for it can be found in Chinese cookbooks or by searching with your favorite search engine. Although some people may think of a very specific dish when they think of lo mein, the name is actually a term for a method of preparing noodles; people can use any sort of ingredients or sauce.
In Chinese, mein are noodles, and lo mein are “tossed noodles,” a reference to the fact that the noodles are added to a stir fry wok at the very end of the cooking process. As a result, the noodles stay soft, and they absorb the sauce that the rest of the food is cooked in. In some regions, lo mein isn't even fried; it's made more like a noodle soup than a stir fry dish. By contrast, chow mein is made with noodles which are fried first so that they are crunchy and crispy.
To make lo mein, all you need is noodles, vegetables and meats of choice, and a sauce. Traditionally, the Chinese use egg noodles made from wheat for this dish, although the noodles can be any shape or size. The noodles should be cooked in boiling water until they start to soften and then drained; run cold water over the noodles to prevent sticking. While the noodles are cooking, you can chop ingredients for the stir fry.
Some common ingredients are ginger, garlic, water chestnuts, scallions, peas, carrots, onions, broccoli, bok choy, and mushrooms, though not necessarily together, and you are certainly free to improvise. You can add protein in the form of meats, seafood, or tofu as well. Fry the ingredients lightly; for best results, fry them separately in the wok in batches to ensure that everything is fully cooked.
Once all your add-ins are cooked, toss them together with your sauce, and then add the noodles to make lo mein. Cook until the noodles are warmed through, and serve immediately. You can use shredded vegetables or preserved meats for a garnish, or serve your lo mein straight.