basics for a juicy burger
1. 75-25% 80-20%. Thats it. Any leaner, and the rarest will still be dry. Fat is juice and fat is flavor. End of discussion
2. handle as little as possible. Quickly make a ball, flatten it out, and cook. Handle it a lot and you got a round flat meatloaf.
3. Griddle a burger, not chargrill. A burger is a different animal griddle cooked. You might convince me that a wood or charcoal fired burger is up there, but a gas charbroiler is inferior. Too crusty and not as juicy.
4. Never, ever, ever, squish a burger while it is cooking. If you griddle a 25% fat burger until well done, it will still be juicy. No blood, just juice.
5. High heat. Sears the outside and makes it juicy.
6. Fry a burger and cover it with a cover to fry-steam it. I am not a steam burger fan, but it is very, very juicy.