The Obvious: Choose the right meat: When it comes to hamburgers, ground round or chuck is the only way to go, and if you've ever heard the saying "fat is where the flavour is," then you understand why. Ground round is a good choice for pan-seared burgers because it has enough fat (10% to 15%) to keep the meat moist but not so much that the burger ends up swimming in melted fat in the pan. For grilled burgers, ground chuck is best. At 15% to 20% fat, it's able to withstand the intense heat of the grill and still make for a mouthwateringly juicy burger. Excess fat simply drains through the grill grate.
Cook extra flavourings first: Smooth out the flavour of garlic, onions, and chiles by gently cooking them and then cooling them slightly before mixing them into the beef. You can toast any spices you want to use at the same time: Cook the aromatics over medium-low heat in a tablespoon or two of oil until they soften, and then add spices and cook briefly until they become fragrant. Add salt and pepper directly to the meat (even if you're not using any other flavours).
Use a light hand: The worst thing you can do to a burger is mash and compact it into shape. Too much pressure makes a dense, heavy burger. Instead, wet your hands to keep the meat from sticking to them, and then gently pat the meat into patties. Make a deep impression in the centre of each patty; this helps the burger cook evenly and keeps it from plumping into a flying saucer shape as it cooks.
Cook it safely: It's an unfortunate part of modern life that we have to be cautious with ground meat, but the grinding process increases the chance of bacterial contamination. If you want to be on the safe side, cook burgers to a minimum of 71°C (160°F). That's medium well, but if you've used the right meat (see above), your burger will still be juicy and delicious.