Krispykreme04 had some good suggestions, here's what I think is crucial:
1. Start with hamburger meat of around 80-85% lean (20-15% fat). If you use fatter meat and fry it in a pan you wind up with the burgers swimming in fat. If you use leaner meat, the burgers are likely going to be dry and tasteless or tough.
2. Krispykreme is right about over working the meat. Spread the meat out in a bowl and add the seasonings. I use a few drops of Worchestershire, onion powder is a must, salt and pepper, garlic powder and a modest amount of cayenne.
3. Preheat the pan to a very high heat. The goal is to immediately sear the beef. It should sizzle the moment the burger touches the metal. Leave it alone for about two minutes then flip it, leave it alone for a minute or two then turn the heat down. The searing helps form that delicious taste. It even has a name, the Milliard effect.
4. Use cheese. A cheeseburger is just better than a burger.