The bacon is evenly browned or deep red-brown
The fat has turned translucent and rendered
The edges look crisp
The bacon has reached your desired texture, from chewy to crisp
It is no longer pale or rubbery
It sizzles less as most of the fat has cooked out
It lifts easily from the pan or tray
For safety, it has reached an internal temperature of 145°F (63°C) if measured