Searing meat caramelizes the natural sugars, enhancing flavor, and seals in the juices. (There is debate about the latter - it more than likely simply hastens the process of forcing the juices into the center of the meat. See resting for more information). It also enhances color for great presentation. This is ideal for steaks which are briefly seared at up to 1200 degrees at steak houses, and now in your own backyard if you own a grill with an infrared searing unit. It works well with most cuts of meat if you are careful not to overcook, especially seafood.
Regular gas and charcoal fires cannot reach these high temperatures but can still be used to create a more than acceptable sear. Kamado style cookers such as the Big Green Egg can reach temperatures of over 800 degrees and are also great for searing meats.
Searing works best if you do not marinade as it may burn and you want to avoid any piercing of the meat which is part of the marinating process. Never use a fork to turn a cut of meat that you are searing as you will lose the benefits of sealing in the juices.
Remove the meat from the refrigerator and let rest at room temperature for at least 30 minutes but not longer than an hour. Pat dry and sprinkle with salt and pepper or your favorite spices/rub.
While I often use oil to coat meat I'm grilling, avoid it if searing meat at high temperatures as the oil will burn. If you do use oil, use an oil that has a high smoke point such as corn, peanut, canola or coconut. Avoid butter and olive oil, especially extra-virgin as it has a very low smoke point. For steak, you can always add a little butter to the cooked steak as it rests before plating.
Blackening is similar to searing and usually does involve high heat, butter, and other spices, often Cajun, but be very careful not to burn. It can literally take a mere 30 seconds per side with certain types of fish, which is easily overcooked.
Braising is also similar to searing but generally done indoor with a very hot pan, then the meat is finished in the oven or crock pot.
Place the cut of meat directly over a very hot fire, and turn 90 degrees after 90 seconds. This will create the signature grill marks you see at high end steak houses. After another 90 seconds flip the meat over and repeat. Shorten the time for seafood.
You can then lower the temperature or move to a cooler part of the grill and cook to desired doneness. Be sure to let the meat rest at room temperature for 10 minutes before serving so that the juices redistribute throughout the meat. Remember, never puncture or press down on the meat, such as a burger, as you will lose the juices.